Download Eradication of invasive alien vertebrates in the UK Overseas

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Eradication of invasive alien vertebrates in the UK
Overseas Territories
A prioritised framework for island restoration to enable the UK Overseas
Territories' Biodiversity Strategy
June 2014
The Royal Society for the Protection of Birds (RSPB)
Funded by the Department for Environment, Food and Rural Affairs
(Defra)
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Contents
EXECUTIVE SUMMARY .............................................................................................................................. 4
ACKNOWLEDGEMENTS ............................................................................................................................. 7
INTRODUCTION........................................................................................................................................... 9
Aims ........................................................................................................................................................ 10
Scope ...................................................................................................................................................... 11
Limitations ............................................................................................................................................... 12
METHODS .................................................................................................................................................. 14
Data collection ......................................................................................................................................... 14
Island Prioritisation .................................................................................................................................. 16
RESULTS .................................................................................................................................................... 21
Islands in the OTs ................................................................................................................................... 21
Beneficiary species in the OTs................................................................................................................ 21
Invasive Species in the OTs.................................................................................................................... 23
Priority Islands ......................................................................................................................................... 25
TERRITORY-SPECIFIC ACCOUNTS ........................................................................................................ 29
ANGUILLA................................................................................................................................................... 30
BERMUDA .................................................................................................................................................. 32
BRITISH INDIAN OCEAN TERRITORY ..................................................................................................... 33
BRITISH VIRGIN ISLANDS ........................................................................................................................ 35
CAYMAN ISLANDS .................................................................................................................................... 37
FALKLAND ISLANDS ................................................................................................................................. 39
MONTSERRAT ........................................................................................................................................... 41
PITCAIRN ISLANDS ................................................................................................................................... 42
SAINT HELENA, ASCENSION AND TRISTAN DA CUNHA ...................................................................... 43
SOUTH GEORGIA AND THE SOUTH SANDWICH ISLANDS .................................................................. 45
TURKS AND CAICOS ISLANDS ................................................................................................................ 46
NEXT STEPS .............................................................................................................................................. 48
ANNEX 1 – Present and Historical Breeding Status full definitions ............................................................ 50
ANNEX 2 – Full List of Beneficiary Species................................................................................................ 52
ANNEX 3 – Full List of Invasive Alien Vertebrates ..................................................................................... 58
REFERENCES ............................................................................................................................................ 61
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EXECUTIVE SUMMARY
The UK Overseas Territories (OTs) are of considerable importance for biodiversity, holding
an estimated 90% of the UKs total biodiversity and over 300 globally threatened species
(IUCN 2013). One of the most serious threats identified to this biodiversity is the presence of
invasive alien species, in particular invasive mammals and other vertebrates (Hilton and
Cuthbert 2010). Invasive vertebrates have been responsible, wholly or partially, for the
extinction of eight endemic bird species and for population declines of numerous other native
bird and reptile species on OTs (BirdLife 2009; Cuthbert and Hilton 2004; Mitchell et al.
2004). As such, the control, eradication and prevention of establishment of invasive alien
species is a key strategic priority in the current OTs Biodiversity Strategy (Defra 2009).
Due to the detrimental impact of Invasive Alien Vertebrates on many native island species,
eradicating invasive alien vertebrates from islands has become an important management
tool to preserve endemic island biodiversity. As eradication techniques have been developed
and refined, the number of islands where eradication is possible and would provide a
biological conservation benefit is increasing (Brooke et al. 2007). The OTs include a wide
range of islands, hosting numerous invasive alien vertebrates as well as native threatened
and endemic species. Until now islands selected for eradication and restoration have
generally been identified opportunistically, without comparative assessment between islands
to weigh the biological benefit of eradicating invasive species, the feasibility and
sustainability of restoration. This study provides a strategic assessment to rank all of the
OTs’ islands according to the greatest biodiversity benefit resulting from technically feasible
invasive vertebrate eradications. This island priority list can then be used to direct actions
and make best use of limited resources to support the strategic priorities of the UK Overseas
Territories Biodiversity Strategy.
Scope and Limitations
The study focussed on the 11 island OTs: Anguilla; Bermuda; British Indian Ocean Territory;
British Virgin Islands; Cayman Islands; Falkland Islands; Montserrat; Pitcairn Islands; Saint
Helena, Ascension and Tristan da Cunha; South Georgia and the South Sandwich Islands
and Turks and Caicos Islands. The Cyprus SBAs, Gibraltar and British Antarctic Territory
were not included. The potential biodiversity gains of an invasive vertebrate eradication were
calculated against a subset of native fauna: all Critically Endangered, Endangered,
Vulnerable and Near Threatened terrestrial vertebrates; marine turtles; restricted-range bird
species and colonial seabird species. Other taxonomic groups were not included as
information on their occurrence, distribution and vulnerability to invasive alien vertebrates is
not currently available in sufficient detail for all of the OTs.
All terrestrial invasive alien vertebrates were included and the logistical feasibility of
eradicating them was assessed for each island and incorporated along with the natural
reinvasion risk for rodents. Social feasibility, socio-economic impacts and the anthropogenic
reinvasion risk of invasive alien vertebrates were not considered in the study as data was not
available in sufficient detail for all islands across the OTs. Island area was not incorporated
into the prioritisation, because it mostly affects the cost rather than the feasibility of an
eradication, with costs factoring into the planning stage of an eradication rather than the
strategic assessment.
Prioritisation Method
Calculating the priority islands was a multi-step process. First, Potential Conservation Value
scores were calculated for each island. This is the maximum conservation value achievable
if all invasive alien vertebrates present could be successfully eradicated. The Potential
Conservation Value incorporates the threat status, irreplaceability and vulnerability to
present invasive vertebrates for all native species on an island.
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Secondly, invasive alien vertebrate species that could technically be eradicated from each
island were identified, using human population size as a criterion for technical feasibility, as
well as natural re-invasion risk as guidance for which eradications would yield lasting
benefits (eradications where natural re-invasion was considered very likely were excluded).
The identified species were then theoretically removed from each island, and a Posteradication Conservation Value was calculated for each island using the same approach as
above with a reduced subset of invasive vertebrates remaining on each island.
The Actual Conservation Value for each island was the difference between Potential and
Post-eradication Conservation Values. This value would be 0 for islands where no invasive
alien vertebrates can be eradicated, and very high for islands where many globally
threatened and /or endemic species are threatened by invasive alien vertebrates which
could all be eradicated.
The island with the highest Actual Conservation Value was considered to be the island with
the highest eradication priority.
Results
One hundred and ninety-one islands (of 2499) harboured at least one native threatened or
endemic vertebrate species and one invasive alien vertebrate (IAV) that was considered to
have a negative impact on a native species.
In total, 217 native (beneficiary) species were considered, of which 18 are Critically
Endangered, 22 Endangered and 26 Vulnerable. Reptiles were the most numerous group
with 27 globally threatened species and another 32 species that are not yet assessed by the
IUCN.
In total, 85 IAV exist in the study OTs, 30 reptiles, 26 birds, 23 mammals and six
amphibians. Rats (Rattus sp.) were the most widespread invasive alien vertebrate species
occurring on 470 islands across all the OTs and recorded from another 282 from which they
had either been extirpated or where they were currently subject to an on-going eradication.
Ten of the 11 OTs in this study have islands in the top 25 priority islands for restoration when
ranked by Actual Conservation Value. The majority of islands in the top 25 are from the
Caribbean Territories. This is due primarily to the rich endemic reptile fauna found on these
islands.
Gough Island in the Tristan da Cunha group is the top priority island restoration project in the
OTs due to the presence of a large number of globally threatened and globally important
breeding seabird species, two endemic land birds and the high impact of predatory house
mice (Mus musculus).
A number of islands including Cayman Brac and St Helena have very high Potential
Conservation Values but do not appear in the final list of priority restoration projects because
some invasive alien vertebrates cannot be eradicated given the human population size. In
these situations eradication or control of some invasive alien vertebrates could still be very
beneficial.
This list is based on current information and knowledge. As more information is collected,
the prioritisation should be updated. A number of OTs, particularly in the Caribbean, would
benefit from further surveys to establish the distribution and impacts of IAV within the
Territory.
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Summary of the Top 25 priority islands for invasive vertebrate eradication ranked by Actual
Conservation Value.
Rank
Island
OT
Invasive Species to be
removed (feral populations
only)
Mice
Examples of native species
that could benefit
1
Gough
2
Anegada
Saint Helena, Ascension
and Tristan da Cunha
British Virgin Islands
Anegada ground iguana,
Anegada skink
Pitcairn Islands
Cats, dogs, goats, cattle,
donkeys, mice, feral pigs,
green iguanas, rats
Cat, dogs, mice, rats, green
iguanas
Rats
3
Little Cayman
Cayman Islands
4
Henderson
5
Guana
British Virgin Islands
Dogs, cats, sheep
6=
Tristan da
Cunha
Norman
Cotton Cay
Necker
Saint Helena, Ascension
and Tristan da Cunha
British Virgin Islands
Turks and Caicos
British Virgin Islands
Mice, rats, sheep
Turks and Caicos
Rats, cats
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Big Ambergris
Cay
South Georgia
Rats, mice
12 =
Pitcairn
South Georgia and the
South Sandwich Islands
Pitcairn Islands
12 =
Jost van Dyke
British Virgin Islands
12 =
Turks and Caicos
15
Little
Ambergris Cay
Salt Cay
Rats, cats, dogs,goats, pigs,
mongooses
Chickens, rats
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17
18
19
20
New
French Cay
Little Tobago
Peter
Ascension
21
Dog
Falkland Islands
Turks and Caicos
British Virgin Islands
British Virgin Islands
Saint Helena, Ascension
and Tristan da Cunha
Anguilla
22
23
Salt
Montserrat
British Virgin Islands
Montserrat
24
25
Great Dog
Ile de la Passe
British Virgin Islands
British Indian Ocean
Territory
6=
8=
8=
10
Turks and Caicos
Rats, dogs, goats
Rats, goats
Rats
Rats, cats, goats
Cattle, dogs, donkeys, cats,
rats, mice
Rats, cats, mice, rabbits
Rats, mice
Goats, rats
Green iguanas, cats, chickens
Rats, mice, rabbits, sheep,
donkeys
Goats
Goats, chickens
Cattle, goats, donkeys, sheep,
pigs
Rats, goats
Rats
Gough bunting, Tristan albatross
Sisters Islands rock iguana
Henderson petrel, Henderson
fruit dove
Mona Island boa, Hawksbill
turtle
Atlantic petrel, Atlantic yellownosed albatross
Virgin Islands bronze skink
Turks Island skink
Lesser Virgin Islands skink,
Virgin Gorda blindsnake
Caicos Islands skink, Bastion
Cay curlytail lizard
White-chinned petrel, other
breeding seabirds
Pitcairn reed warbler, breeding
seabirds
Mona Island boa
Hecht's Caribbean gecko
Turks and Caicos rock iguana
Many breeding seabirds
Turks and Caicos rock iguana
Virgin Islands bronze skink
Hawksbill turtle
Ascension frigate bird, other
breeding seabirds
Anguilla Bank skink, Anguilla
Bank ameiva, breeding seabirds
Lesser Virgin Islands skink
Montserrat oriole, mountain
chicken frog, galliwasp (lizard)
Virgin Islands coqui (frog)
Breeding turtles and seabirds
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ACKNOWLEDGEMENTS
This study was funded by the UK Government’s Department for Environment, Food and
Rural Affairs (Defra). It would not have been possible without the help and assistance from a
wide range of people and organisations. Within the Royal Society for the Protection of Birds
(RSPB) particular thanks goes to the OTs Unit of Clare Stringer, James Millett and Jonathan
Hall for their continued assistance and guidance, and in Conservation Science Steffen Oppel
and Richard Cuthbert for advice on developing the methodology, creating the R code for
analysis and in reviewing the report.
Many thanks go to Stuart Butchart and Jez Bird (BirdLife International) and Nick Holmes
(Island Conservation) for their considerable support and assistance in developing the
methodology and data protocols. Dena Spatz and Kelly Newton (University of California,
Santa Cruz) for assistance in data collection protocols and GIS; Andrew Budden (RBG-Kew)
for collating all of the Falkland Islands data; Richard Lewis (RBG-Kew/ Falklands
Conservation) and Rebecca Upson (RBG-Kew) for assistance with collating information on
endemic and invasive plant species in the Falkland Islands.
Finally, many thanks go to the Project Advisory Group members for their useful input,
comments and guidance at various stages during the study and all of the Territories’
Government Departments and Territory NGOs for their cooperation in providing and verifying
much of the information necessary to carry out this study.
Anguilla
Department of the Environment, Government of Anguilla
Anguilla National Trust
Ascension
Ascension Conservation Department, Ascension Island Government (Stedson Stroud,
Jolene Sim, Nathan Fowler)
Bermuda
Department of Conservation Services, Government of Bermuda (Andrew Petit, Alison
Copeland)
British Indian Ocean Territory
Pete Carr
British Virgin Islands
Department of Conservation and Fisheries, British Virgin Islands Government (Mervin
Hastings)
British Virgin Islands National Park Trust (Nancy Woodfield Pascoe)
Cayman Islands
Department of Environment, Cayman Islands Government
National Trust for the Cayman Islands (Paul Watler)
Falkland Islands
Environmental Planning Department, Falkland Islands Government (Nick Rendell)
Falklands Conservation (James Fenton, Kalinka Rexer-Huber)
Sally Poncet
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Montserrat
Department of the Environment, Government of Montserrat
Pitcairn Islands
Pitcairn Natural Resources Division, Pitcairn Islands Government (Michele Christian)
Saint Helena
Environmental Management Directorate, St Helena Government
St Helena National Trust
South Georgia and the South Sandwich Islands
Government of South Georgia and the South Sandwich Islands (Jennifer Lee)
Tristan da Cunha
Tristan da Cunha Conservation Department, Tristan da Cunha Government (Trevor Glass,
Katrine Herian – RSPB)
Turks and Caicos Islands
Department of Environment and Coastal Resources, Turks and Caicos Islands Government
(Eric Salamanca, Bryan Naqqi Manco)
Turks and Caicos National Trust (Ethlyn Gibbs-Williams)
Dr Glenn Gerber – Institution for Conservation Research, San Diego Zoo
Project Advisory Group
Jez Bird – BirdLife International
Lord David Blencathra – Cayman Islands Government Representative in the UK
Sarah Brennan – UK Executive Officer Falklands Conservation
Jeff Dawson - RSPB
Kimberley Durrant – UK Representative for the Government of Bermuda
Siôn Griffiths – Foreign and Commonwealth Office
Richard Lewis – RBG-Kew and Falklands Conservation
Dennison Miller – Cayman Islands Government Representative in the UK
James Millett - RSPB
Janice Panton MBE – Government of Montserrat UK Representative
Trevor Salmon – Department for Environment, Food and Rural Affairs, Defra
Clare Stringer - RSPB
Tony Weighell – Joint Nature Conservation Committee, JNCC
Kedell Worboys MBE – St Helena Government UK Representative
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INTRODUCTION
The UK Overseas Territories (OTs) are: Anguilla; Bermuda; British Antarctic Territory; British
Virgin Islands; Cayman Islands; Falkland Islands; Gibraltar; Montserrat; Pitcairn Islands;
Saint Helena, Ascension and Tristan da Cunha; South Georgia and the South Sandwich
Islands; Turks and Caicos Islands and the Sovereign Base Areas on Cyprus.
The OTs are of considerable importance for biodiversity, holding an estimated 90% of
biodiversity for which the UK is responsible and more than 300 globally threatened species
(those assessed as Critically Endangered, Endangered or Vulnerable on the IUCN Red List;
IUCN 2013)1. The number of endemic species in the OTs was estimated as over 300 (Defra
2012) but with over 400 invertebrates on Saint Helena alone this is likely a gross
underestimate (RSPB 2013, unpublished data). In relation to birds, the OTs hold 33 of the
UK’s 36 globally threatened species placing the UK 19th in the world for numbers of globally
threatened bird species ahead of South Africa and Madagascar (Sanders ed. 2008).
Seventy-eight Important Bird Areas have been identified in the OTs holding globally and
regionally important breeding areas for a number of seabird species. These include arguably
some of the most important seabird breeding colonies in the world such as Gough Island in
the South Atlantic which is home to millions of breeding seabirds and is the major breeding
site of the Critically Endangered Tristan albatross (Diomedea dabbenena).
In addition to the native fauna and flora, over 2000 non-native invasive alien species (IAS)
have been recorded in the OTs (Defra 2012). IAS are species whose introduction and/or
spread outside their natural present or past distribution threatens biodiversity (IUCN 2000).
Humans have and continue to introduce IAS, either accidentally or deliberately, with many
historical introductions commencing around the same time as European exploration in the
16th Century (Hilton and Cuthbert 2010). IAS are recognised as one of the main threats to
biodiversity globally, particularly on islands (IUCN 2000). The issue of IAS is a key target
(Aichi Target 9) and a cross-cutting theme in the Convention on Biodiversity 2011-2020
Strategy. The control, eradication and prevention of establishment of IAS is also a key
strategic priority of the current OTs Biodiversity Strategy (Defra 2009).
The impacts of IAS are wide-ranging and include direct predation on and competition with
native species; habitat modification; transmission of disease to both native species and
livestock; and economic impacts such as crop damage. Globally some of the most damaging
IAS are vertebrates (from here on “IAV”) and in particular mammals. Invasive rodents
(notably rats Rattus spp. and house mouse Mus musculus) occur on over 80% of oceanic
islands (Russell et al. 2008a) and pose a significant threat to island biodiversity (e.g.
Courchamp et al 2003; Jones et al. 2008). Globally, feral cats (Felis catus) have contributed
to at least 14% of all bird, mammal and reptile extinctions and the decline of at least 8% of
Critically Endangered birds, mammals and reptiles (Medina et al. 2011). Other predators
such as feral dogs (Canis familiaris), feral pigs (Sus scrofa) and small Asian mongooses
(Herpestes javanicus) are also serious threats with the latter having a major role in the
extinction, extirpation and decline of many Caribbean reptile species (Henderson 1992;
Powell and Henderson 2005; Hays and Conant 2007). Alongside predators, feral livestock
and in particular goats (Capra hircus) can have drastic effects on island ecosystems altering
native habitats through herbivory; spreading non-native plant seeds and exacerbating soil
erosion (Coblentz 1978).
Other IAV introduced to islands include numerous bird, reptile and amphibian species. A
potentially serious issue in the Caribbean is the introduction of alien reptile and amphibian
1
The Red List data used for this report was the 2012 list (before the 2013 update was applied). The
Red List categories mentioned in this report may therefore not be the current categories.
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species leading to competition with and predation of native species (Henderson 1992; Pitt et
al. 2005; Platenburg 2007). Introduced amphibians also pose another threat by acting as
possible carriers and source populations for infectious diseases, such as the fungal disease
chytridiomycosis and ranavirus, with the former being arguably the greatest known global
disease threat facing any vertebrate group (Wake and Vrendenburg 2008).
The negative impacts of IAV are known and have been documented across a range of OTs.
Of the 10 endemic bird extinctions in the OTs since 1500, eight have been wholly or partially
due to IAV (BirdLife 2009). Native rock iguanas (Cyclura spp.) in the Cayman Islands, British
Virgin Islands and Turks and Caicos Islands have suffered population declines in part as a
result of feral dog, cat and livestock populations (Iverson 1978; Gerber 1995; Mitchell et al.
2004). Even IAV usually considered less damaging to most native species, such as house
mice, have in recent times shown they can evolve devastating predatory behaviour such as
observed on Gough Island (Cuthbert and Hilton 2004; Wanless et al. 2007).
The eradication of IAV from islands where they are having a damaging impact can result in
dramatic recoveries of native species. The eradication of feral cats from Ascension Island
between 2002 and 2004 has led to six seabird species recolonising the island, including the
Vulnerable Ascension frigatebird (Fregata aquila) in 2012 (Ratcliffe et al. 2009b; pers.
comm. Ascension Island Government Conservation Department). On Mokoli’i Island in
Hawaii the eradication of rats led to the survival rate of wedge-tailed shearwater (Puffinus
pacificus) chicks increasing from one per year pre-eradication to 185 per year in only two
years post-eradication (Smith et al. 2006). After removing feral goats and pigs from Sarigan
Island in the Northern Mariana Islands there was an increase in plant species richness and
in skink numbers (Kessler 2002).
The ability to effectively remove IAV from islands is improving as techniques continue to be
developed and refined, meaning that the number of islands where IAV eradication is
possible and would provide a conservation benefit is increasing (Brooke et al. 2007). This
applies to the OTs which comprise a range of islands, IAV, threatened and endemic species.
The biological need must be weighed against the feasibility and sustainability of an operation
to make best use of the limited resources available. Undertaking a prioritisation exercise for
eradication of IAV in the OTs at this time will provide a robust information base to direct
actions and resources to support the strategic priorities of the UK Overseas Territories
Biodiversity Strategy.
Aims
The aim of this study was to:
1.
2.
3.
4.
5.
Produce a robust priority list of islands for IAV eradications in the OTs based on
potential biodiversity gains, IAV eradication feasibility and natural reinvasion risk of
rodents.
Identify island management units for future eradications and for islands where
incorporating appropriate biosecurity measures into an eradication programme should
be considered a priority.
Identify data gaps that hamper a full assessment of island restoration priorities, in
particular on IAV occurrence, distribution and abundance.
Identify specific IAV or beneficiary species concerns within individual OTs.
Provide a checklist of next steps to consider when planning to undertake an eradication
project.
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Limitations on this study:
1.
2.
3.
The priority list is based on current information and knowledge. As information is
updated and collected the prioritisation should be repeated.
The study only incorporates a subset of native biodiversity and IAS (see below and
methods). Additional native taxonomic groups and IAS can be incorporated in future
prioritisations as information and knowledge improves.
The study does not aim to provide advice on eradication methodologies or biosecurity
measures.
Scope
The scope of the study was dictated by the level of information available and what could be
reasonably collected in the six month timeframe of the study.
The study focused on the 11 island OTs: Anguilla; Bermuda; British Indian Ocean Territory;
British Virgin Islands; Cayman Islands; Falkland Islands; Montserrat; Pitcairn Islands; Saint
Helena, Ascension and Tristan da Cunha; South Georgia and the South Sandwich Islands
and Turks and Caicos Islands (see Figure 1).
Pitcairn Islands
Figure 1 Map of the 11 OTs included in the study. NB that Saint Helena, Ascension and
Tristan da Cunha constitute a single Territory
Gibraltar was not included in the study as it is on mainland Europe making any eradication
not feasible or sustainable. British Antarctic Territory was omitted as currently it has no
terrestrial IAV present. Also excluded were the Cyprus Sovereign Base Areas as they are
part of a much larger island and therefore not appropriate for eradication prioritisation in this
instance.
Various eradication prioritisation exercises have been carried out previously, again focusing
on different spatial scales, however these have mostly focused on a single native species
group - seabirds (for example Brooke et al. 2007; Ratcliffe et al. 2009a; Capizzi et al. 2010;
Harris et al. 2012). Few have looked at incorporating multiple native taxa (see Ecosure
2009) perhaps due to the lack of information regarding population trends in other taxa when
compared to seabirds. Incorporating other taxonomic groups is an important consideration
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for the OTs as they harbour a number of threatened and endemic species, particularly
reptiles. Concurrently Island Conservation in partnership with BirdLife International are
undertaking a global analysis of island eradication priorities. Although the scope of this
global analysis is slightly different, the respective methodologies have been devised in
consultation between the RSPB, Island Conservation and BirdLife International. This will
ensure that the underlying methods and categories are consistent between methodologies.
The potential biodiversity gains of an eradication programme were assessed against a
subset of native fauna. Specifically these were: all Critically Endangered, Endangered,
Vulnerable and Near Threatened terrestrial vertebrate species (including marine turtles) as
defined by the IUCN Red List (IUCN 2012); all restricted-range bird species (defined as an
A2 species by BirdLife International) and all colonial seabird species and any other Important
Bird Area trigger species. Also included were various reptile species occurring in the
Caribbean OTs that have not yet been assessed by IUCN (see methods for selection
criteria) as reptiles are an important component of Caribbean biodiversity (Procter and
Fleming 1999). Other taxonomic groups were not included as information on their
occurrence, distribution and how IAV impact upon them is not currently available in enough
detail for all of the OTs.
As with native fauna only terrestrial IAV were considered in the study as these are the IAS
whose distribution and impact upon native fauna is best known and, for at least some
groups, eradication methodologies exist. All invasive invertebrates, freshwater and marine
species and plants were omitted as information on their distribution and impacts is poorly
known compared to IAV and not equally known across the OTs.
Limitations
Due to the time scale of the study and the level of information available across all the OTs,
some factors were excluded from the study, these being:
1.
2.
3.
4.
Social feasibility i.e. how likely it is that Governments and especially local
communities/island owners would support eradications on islands. Having the support or
at least agreement of local communities is an essential component of any eradication
programme (Oppel et al. 2011). This is likely to vary considerably between and within
OTs and requires detailed analysis into people’s values and views surrounding IAV and
their removal along with continued consultation and engagement. As such, this should
be assessed prior to any proposed eradication on an island by island basis.
Anthropogenic reinvasion risk. This is the likelihood of IAV being introduced onto islands
either accidentally or deliberately by human activity such as tourists visiting islands and
boat landings. This is a potentially important factor and has been incorporated into some
previous prioritisation exercises (Capizzi et al. 2010; Harris et al. 2012). Both of these
exercises however focussed on a single country with sufficient detailed information to
allow suitable proxy criteria for anthropogenic reinvasion risk to be developed. The level
of information to allow this to be applied equally across all of the OTs was not readily
accessible for all OTs within the study time scale.
Socio-economic impacts of IAV. As well as impacting upon native biodiversity IAV can
have negative socioeconomic impacts in a variety of areas including agriculture, tourism
and water quality (Reaser et al. 2007). The level of information required across all of the
OTs to incorporate this into the study was too detailed and complex to collect within the
time frame of the study.
Island area was not considered a limitation to feasibility in this study as cost is the
primary limiting factor in undertaking large island eradications. Whilst cost effectiveness
is incorporated into many prioritisation exercises it can be argued that the initial
prioritisation should be based on the potential conservation value of an eradication with
costs being factored into the planning stage once the necessary detailed information
has been collected (Harris et al. 2012). As methods improve and new techniques are
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5.
developed the size of islands where IAV can be effectively eradicated will increase and
the cost will most likely decrease in the future.
In relation to point 4 the distribution of IAV and beneficiary species on an island was not
incorporated into the prioritisation and it was assumed that all IAV and beneficiary
species present on the island were distributed across the whole island. This will not be
true in many cases, but to incorporate distribution information into a prioritisation would
require detailed information which is currently not available for all islands within the OTs.
It is also considered important for the prioritisation to highlight islands where there is
potential for IAV to impact upon beneficiary species so that proactive action can be
taken.
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METHODS
Data collection
The eleven island OTs were included in the study, these being: Anguilla; Bermuda; British
Indian Ocean Territory; British Virgin Islands; Cayman Islands; Falkland Islands; Montserrat;
Pitcairn Islands; Saint Helena, Ascension and Tristan da Cunha; South Georgia and the
South Sandwich Islands and Turks and Caicos Islands. Gibraltar, the British Antarctic
Territory and the Cyprus Sovereign Base Areas were not included in the study.
For each of the eleven OTs data was collected in three main categories: physical and social
information for each island; data on all beneficiary species and data on all terrestrial IAV. All
internet and document sources from which data was obtained are listed in the reference
section.
Island Information
A list of islands in the OTs was compiled, firstly through using the updated version of the
Global Island Database (GID) created by the United Nations Environment Programme –
World Conservation Monitoring Centre (UNEP-WCMC 2013).The GID, comprising a global
vector layer of islands, is housed and maintained by UNEP World Conservation Monitoring
Centre, Cambridge, UK (www.unep-wcmc.org). The GID is originally based on Open Street
Map (using a 1:75,000 Landsat product from the US National Geospatial - Intelligence
Agency) and has been substantially refined through the work of a number of organisations
(e.g. UNEP-WCMC, Island Conservation, BirdLife International, the RSPB, IUCN/SSC ISSG,
PIER, Global Island Network). The GID is an intermediate product that is continuously being
refined by the user community.
Whilst the GID is a good starting point for compiling a list of islands in the OTs, it is not a
complete data set. Additional islands were added to this database from a variety of sources
including: Google Maps; territory-held GIS layers and the South Georgia GIS (British
Antarctic Survey 2008 www.sggis.gov.gs). All islands were given a unique numerical island
code. For each island in the OTs the following information was collected:
Island name: the commonly used name was recorded when known; using information from
Government departments, NGOs within the OTs, various reports, publications, documents
and internet sources such as Wikipedia. If there are multiple names commonly used these
were also recorded, e.g. Amy Island / Outer Knob.
Latitude, Longitude and area: these were all taken from the GID layer in ArcGIS 10.1, with
the exception of the Falkland Islands, for which information was taken directly from the
Falklands Island Database (Falklands Island Government 2012).
Human population: information was collected on the presence of human habitation, human
population size and human habitation type. Information was obtained from Government
Census reports; Government departments; Wikipedia and other internet sources. Presence
of human habitation was classified as: Yes, No or Unknown. Human population size was
categorised into minimum and maximum ordinal categories of: None, Unknown, 1-10, 11100, 101-1000, 1001-10000 and >10000. When known, actual population figures were also
recorded. For most individual islands within the OTs, population figures were not available
as census data usually refer to the Territory as a whole. In these cases satellite imagery
from Google Earth was used to estimate the ordinal category for population size based on
the number of buildings on the island. Each building was estimated to house between one
and four inhabitants. Therefore, an island with 10 dwellings would be assigned a minimum
category of 1-10 and maximum category of 11-100.
14
The type of human habitation was assigned to one of the following categories:
 Permanent community: people inhabiting the island all year round in basic or rural but
not urban communities.
 Seasonal community: the island is not inhabited all year round, but only at certain times
of the year e.g. a summer fishing community or a seasonal bar/restaurant.
 Military base: the island is solely occupied by military personnel and associates.
 Research station: the island is solely occupied by research personnel either
permanently or seasonally.
 Multiple use: the island is occupied for multiple purposes including urban communities.
This is the typical category for most islands with large human populations.
 None: island is currently uninhabited, though it may have been inhabited in the past.
 Unknown: no information is available regarding human habitation on the island.
Ownership: information on island ownership was collected from Government departments or
publically available internet sources for the purposes of identifying the contact for any future
work on that island. This was classified in one of the following categories:
 Government: island is owned entirely by the respective Territory Government.
 Private single: island is owned entirely by a single private individual, family or group e.g.
National Trust.
 Private multiple: island is community owned or owned by multiple private individuals
 Military: island is entirely owned by the military.
 Mixed: island ownership is a combination of government, private and / or military land
ownership which is the typical case for most of the larger islands.
 Unknown: island ownership status is unknown.
Protection: the protected status of an island was recorded using information from
Government departments and publications. This refers only to Government designated
protected area status and does not reflect any privately protected islands i.e. islands in
private ownership where the owner has designated the island for biological conservation.
The protected status of an island was recorded as either:
 Fully: the island is wholly under a Government protected site designation.
 Partial: the island is partially under a Government protected site designation.
 None: the island has no form of Government protected site designation.
 Unknown: the protected site designation of the island is unknown.
Beneficiary species information
Information was collected on all Critically Endangered, Endangered, Vulnerable and Near
Threatened terrestrial vertebrate species (including marine turtles) as defined by the IUCN
Red List (IUCN 2012) as well as all Least Concern colonial seabird species and restrictedrange bird species (defined as an A2 species by BirdLife International). Also included were a
number of reptiles occurring in the Caribbean OTs that have not yet been assessed by
IUCN. These were selected for inclusion based on the following criteria (following Powell and
Henderson 2012):
1)
2)
Are a Territory endemic species; or
Occur on less than 15 islands across the Caribbean region.
Nomenclature for all beneficiary species followed the IUCN Red List. Data was collected
from a variety of sources including papers, reports and information held by the relevant
government departments within each Territory.
15
For each island the presence of a beneficiary species was recorded in terms of its present
breeding status (defined as being within the last 20 years) in one of the following categories
(for full definitions see Annex 1, which have been developed by Island Conservation, BirdLife
International and University of Santa Cruz):
 Confirmed: the species has been recorded as breeding on the island.
 Probable: the species has not been confirmed but is strongly suspected as breeding on
the island based on supporting evidence such as breeding adult found in mist nets,
used/abandoned nests, acoustic monitoring.
 Potential: unclear records of breeding in the last 20 years but has been recorded as
breeding between 21 and 200 years ago.
 Data Deficient: no information regarding the species breeding status.
 Extirpated: the species is confirmed as being extirpated from the island.
 Non-breeding: the species is confirmed but does not breed on the island (e.g. migratory
birds, seasonal roosting).
In addition, historical breeding status (defined as between 21 and 200 years ago) for the
beneficiary species was recorded in one of the following categories:
 Not Applicable: if current breeding status is recorded as Confirmed.
 Confirmed: the species has been confirmed as breeding on the island historically.
 Probable: the species has not been confirmed but is strongly suspected to have bred on
the island in the past based on supporting evidence (as above).
 Potential: the breeding status of the species in the last 21 – 200 years is unclear.
 Data Deficient: there is no information on the breeding status of the species in the last
21 – 200 years.
Where available, population breeding data was also recorded along with any notes regarding
the species breeding on that island, e.g. is the species an island endemic; restricted to a
particular location on the island or if it is a globally important breeding population.
Invasive species information
For every island information was collected on the presence of IAV. Data was collected from
reports, publications, local Government departments and comments from experts in the
various OTs. Presence was recorded in one of the following categories:
 Confirmed: evidence from literature or experts confirms the presence of the invasive
species on that island.
 Suspected: the invasive species is suspected to be on that island based on evidence
from literature or expert opinion. Also used if evidence states the invasive species is not
established or not reproducing.
 On-going Eradication: invasive species is confirmed as being present on that island and
there is a current eradication (but not control programme) in progress.
 Extirpated: the invasive species was confirmed as present previously but has now been
extirpated due to a successful eradication programme.
 Unknown: the IAV is known to occur in the Territory but due to lack of survey information
it is not known whether it is or is not present on the island.
Island Prioritisation
The final island prioritisation list takes into account the conservation value of eradicating
invasive species from an island; the natural reinvasion risk of islands by rodents and the
logistical feasibility of eradicating various invasive groups from individual islands based on
the human population size and the size of that island. Social feasibility, anthropogenic
reinvasion risk and terrain complexity are not incorporated into the prioritisation exercise as
the level of detailed data required for each was not available for all islands included in the
exercise or possible to collect within the timeframe of the project (see Limitations for further
details).
16
Potential Conservation Value (PCV)
Based on the methodology of Brooke et al. (2007) this represents the conservation value or
biodiversity benefit of eradicating all IAV from an island in order to avoid unforeseen
secondary effects. PCV incorporates three scores:
Threat Status (T): the level of threat facing the beneficiary species based on the IUCN Red
List category and scored using both a logarithmic and linear scale.
IUCN Category
CR
EN
VU
NT
LC
Log Scale
100
10
1
0.1
0.01
Linear Scale
5
4
3
2
1
Unassessed reptile species were categorised as At Risk (AR) and were given a score
equivalent to VU for the purposes of analysis. This was chosen as it is the median score for
threat status though it is acknowledged that it may, in some cases, be an under or
overrepresentation of threat and will need to be adjusted as full Red List assessments are
completed for each species. Caribbean skinks (Family Scincidae), although not officially
assessed on the IUCN Red List, were assigned a category based on the recommendations
made in Hedges and Conn (2012).
Irreplaceability (I): a measure of the global importance of a particular island for a beneficiary
species. Scored for each beneficiary species per island, based on either the total number of
islands supporting the beneficiary species, or the percentage of the species Global Breeding
Population or Regional Breeding Population (GBP and RBP respectively) the island
supports. This was scored using both a logarithmic and linear scale.
Criteria
Log Scale
Linear Scale
Single island endemic or island supports >90% of GBP
100
5
Occurs on 2-5 Islands or island supports 50 – 90% of
10
4
GBP
Occurs on 6-10 Islands or island supports 1-50% of
1
3
GBP or 50 – 100% of RBP
Does not qualify for the above but is a restricted-range
0.1
2
species or island supports 1-50% of RBP, or is a
seabird island listed as an IBA under criterion A4iii
because it is known or thought to hold, on a regular
basis, >10,000 pairs of seabirds of one or more species,
or is globally or regionally important for wintering / nonbreeding congregations of an IBA trigger species
Not any of the above
0.01
1
NB Both log scales for T and I are of the same order of magnitude so as not to weight
priority towards one or the other when combined.
GBP and RBP were primarily assessed using the 2012 BirdLife IBA data. For multiple island
IBAs, containing globally and regionally important breeding populations of a species, each
island population was treated as being part of the GBP or RBP and scored accordingly,
unless information was provided to the contrary. Additional information regarding breeding
population sizes was taken from reports and papers where this had been stated.
17
If a beneficiary species could be categorised into two different scores, e.g. it occurs on three
islands but one of those islands supports over 90% of the GBP, it was given the highest
score for that individual island.
Severity of Impact (S): an estimation of the impact of each type of IAV upon each beneficiary
species on islands where they both occur. Impact was scored as either: 0, 1 or 2 and was
based on either direct evidence of IAV impacts on the beneficiary species or impacts of the
IAV on sister / similar species around the globe. Where there is uncertainty of the level of
impact a worst case scenario was assumed. The impact scoring system comprised:



2 - the IAV is known, suspected or has the potential to have a detrimental impact upon
the beneficiary species causing declines in populations either through direct predation,
habitat modification, competition, spreading of disease etc.
1 - the IAV co-exists with the beneficiary species but is likely to prevent the beneficiary
species from reaching its maximum potential population due to its presence by, for
example, suppressing breeding success or in creating sub-optimal habitat.
0 - no apparent negative impact upon beneficiary species.
Calculating an island’s PCV
For each beneficiary species whose present breeding status was recorded as confirmed or
probable and for those globally important congregations of non-breeding species on that
island, four benefit scores (B) are calculated using the following formulas:
B=TxIxS
The severity of impact (S) score used is the maximum S score affecting that beneficiary
species on that island. For example, if there were three IAV on an island scored as having
an impact of 2, 1 and 1 respectively, the benefit score for that beneficiary species will use
the S score of 2. Only IAV recorded as being confirmed or suspected were considered.
Additional benefit scores were also calculated for those species recorded as potentially
breeding on the island or that were recorded as having confirmed or probable historical
breeding but are now extirpated. This reflects the restoration potential of an island should
IAV be eradicated. These benefit scores were calculated in the same way as above but
divided by 2 to reflect that this is only a potential benefit of eradicating an island through
future recolonisation (either natural or assisted) by those species.
As both threat and irreplaceability are scored on two different scales (log or linear), because
there is currently no consensus on which scale performs better, the benefit score for each
species was calculated in four different ways, using all four possible combinations of log and
linear scores of both threat and irreplaceability. This resulted in four non-comparable
conservation values, which were all used independently for the priority assessment.
18
All the benefit scores for all native vertebrates on an island were then summed to give the
overall island PCV score. The calculation is demonstrated in the example below:
Big Island worked example
Beneficiary
Species
Sp 1
Sp 2
Sp 3
Sp 4
Threat Status
Log
Linear
100
5
10
4
1
3
0.01
1
Irreplaceability
Log
Linear
100
5
1
3
0.1
2
0.1
2
Species 1: B1 = 100 x 100 x 2 = 20000
(log-log scale)
B2 = 5 x 5 x 2 = 50
(linear-linear scale)
B3 = 100 x 5 x 2 = 1000
(log-linear scale)
B4 = 5 x 100 x 2 = 1000
(linear-log scale)
.
PCV1 = (Sp1.B1 + Sp2.B1 + Sp3.B1 + Sp4.B1) = 20000 + 20 + .1 + 0 =
PCV2 = (Sp1.B2 + Sp2.B2 + Sp3.B2 + Sp4.B2) = 50 + 24 + 6 + 0 =
PCV3 = (Sp1.B3 + Sp2.B3 + Sp3.B3 + Sp4.B3) = 1000 + 60 + 2 + 0 =
PCV4 = (Sp1.B4 + Sp2.B4 + Sp3.B4 + Sp4.B4) = 1000 + 8 + 0.3 + 0 =
Severity of
Impact
2
2
1
0
20020.1
80
1062
1008.3
Post-eradication Conservation Value (ECV)
On some islands, it may not be possible to eradicate all damaging invasive species and
therefore the full PCV will not be achieved. To assess the realistic conservation value of
islands, the ECV was calculated for each island using the same methodology as outlined
previously, but only including those IAV species that were considered not feasible to
eradicate at present. When calculating the ECV, the S score used for each beneficiary
species was the highest of those IAV remaining after eradicating all logistically feasible IAV
that were unlikely to recolonise the island naturally.
To determine which IAV could be logistically eradicated from islands, IAV were classified into
six broad categories based on the type of eradication methods used: Rodents (rats, mice
and including lagomorphs like rabbits and hares), Predators (mammalian carnivores),
Ungulates, Iguana (including monitor lizards), Birds and Other reptiles and amphibians.
Logistical eradication feasibility for each class in which an IAV scored a 1 or 2 for impact was
then assessed on an island-by-island basis using the following criteria.
Rodents: eradication not considered feasible on islands with a human population >1000.
Predators, Ungulates, Iguana: eradication not considered feasible on islands with a human
population >10000.
Birds: applies to various bird species. Chicken eradication not considered feasible on all
islands >5km². Eradication of all other bird species e.g. kiskadees (Pitangus sulphuratus),
crows (Corvus sp.) and common mynas (Acridotheres tristis) not considered feasible.
Although it is acknowledged that invasive bird species have been eradicated from small,
isolated islands previously (e.g. mynas in the Seychelles) similar situations do not occur in
the OTs.
Reptiles and amphibians: eradication not considered feasible due to a current lack of
effective methodologies for these species (Pitt et al. 2005; Krause 2009). Two exceptions to
this are cane toads (Rhinella marina) on islands <10ha which has successfully been
achieved in Bermuda and the red-eared slider (Trachemys scripta elegans) freshwater turtle
19
in Bermuda where eradication is considered feasible (freshwater turtles are also present in
other OTs but are not currently considered to impact upon any beneficiary species).
These human population figures are based on analysis done by Island Conservation of
successful eradications from Oppel et al. (2011) and subsequently agreed with internal and
external experts.
Natural Reinvasion Risk (NRR)
The long-term success of an eradication project can be jeopardized by either natural or
human-assisted reinvasion of the eradicated species (Clout & Russell 2008; Russell et al.
2008b; Harris et al. 2012). We considered the reinvasion risk in our prioritization by
excluding an eradication as unlikely to yield lasting benefits i.e. if unassisted reinvasion via
swimming was likely during or soon after an attempted eradication. Several mammals (e.g.,
rodents, mustelids, deer, foxes) can swim between islands and may reinvade islands after
eradication. However, besides rodents the remaining swimming species inhabited very few
islands in our study area, and their reinvasion risk after eradication was negligible for our
overall assessment. Rodent eradication on islands within 2 km of an island assessed as
being unfeasible for rodent eradication was excluded based on the maximum swimming
distance recorded for rodents (Russell et al. 2008a; Russell et al. 2008b). Eradication on
these islands may be technically feasible; however, due to the high reinvasion risk they are
less likely to maintain the benefit of eradication. Therefore we excluded them from our
prioritization.
Actual Conservation Value (ACV)
The ACV was calculated for each island from the corresponding PCV and ECV scores using
the following formula:
ACV = (PCV – ECV)
For each island, we calculated four different ACV scores, based on the different
combinations of log and linear scales in threat and irreplaceability. All islands were ranked
according to their ACV scores, which resulted in four ranks for each island due to the four
combinations of log and linear scales. The median of these four ranks was then taken to
order the islands based on their priority for eradication (see example below). The island with
the lowest median ACV rank was the island that would produce the highest conservation
benefit from IAV eradication.
Final ranking example, the island with the highest eradication priority is highlighted in Red
Island
Big Island
Little Island
Rat Island
Goat Island
Cat Island
Sandy Island
ACV1
Rank
2
6
4
1
5
3
ACV2
Rank
6
5
1
2
3
4
ACV3
Rank
3
5
4
1
2
6
ACV4
Rank
4
3
1
2
5
6
Median ACV
Rank
3.5
5
2.5
1.5
4
5
Final Rank
3
5
2
1
4
5
20
RESULTS
Islands in the OTs
In total 2,499 islands, islets and rock stacks were recorded as being present in the eleven
study OTs, although this figure will likely change as the GIS mapping of the OTs is improved.
The Territory with the most islands is South Georgia and the South Sandwich Islands (n =
1,071, 42.9%).
The total land area covered by these Territories is approximately 17,635 km² with the
Falkland Islands having the greatest land area (approx. 12,000 km², 68%) and East Falkland
the largest single island (6,511 km²). See Table 1 for full details of island physical details.
Table 1 Total number of islands and land area by Territory. St Helena, Ascension and
Tristan da Cunha are listed separately.
Territory
Number of
Islands
Approximate total land
area (km²)
% land area
of total
Anguilla (AIA)
22
79.13
0.45
Bermuda (BMU)
131
55.73
0.32
British Indian Ocean Territory (BIOT)
56
49.99
0.28
British Virgin Islands (BVI)
57
153.78
0.87
Cayman Islands (CYM)
12
270.26
1.53
Falkland Islands (FLK)
853
11,999.80
68.04
Montserrat (MSR)
2
101.58
0.58
Pitcairn Islands (PCN)
22
48.75
0.28
St Helena, Ascension and Tristan da
Cunha
181
400.96
2.27
St Helena (SHN)
103
124.08
0.70
Ascension (ASC)
44
97.80
0.55
Tristan da Cunha (TDC)
34
179.08
1.02
1,071
3,935.82
22.32
92
539.85
3.06
2,499
17,635.44
100
South Georgia and the South
Sandwich Islands (SGS)
Turks and Caicos Islands (TCI)
Total
Only 102 islands (3.3%) are classified as having some form of human habitation. Of these,
73 are classed as having permanent or multiple human habitation types; 25 as being
seasonally inhabited; three solely comprising research stations (Gough, TDC; South Georgia
and Bird Island, SGS) and one as being solely military (Diego Garcia, BIOT). Five islands
have human populations over 10,000 (Anguilla; Grand Cayman; Main Island, BMU;
Providenciales, TCI; Tortola, BVI) and eight others with populations over 1,000.
Beneficiary species in the OTs
In total 217 beneficiary species were included in the analysis. Seabirds accounted for the
majority of these species (n=92, 42.1%) as Least Concern species were only included in the
analysis if they were either a colonial seabird species, restricted-range bird species or an
IBA trigger species (see Table 2 for summary and Annex 2 for a full species list). Sixty-six of
the beneficiary species are listed by IUCN as globally threatened, of which 18 are Critically
Endangered, 22 Endangered and 26 Vulnerable. Reptiles, including four marine turtle
21
species, were the most numerous globally threatened group (n=27, 40.3%; see Table 2 and
Figure 2). Of the globally threatened species considered, four are currently considered to be
extirpated from the OTs (Roosevelt’s giant anole Anolis roosevelti; Puerto Rican crested
toad Peltophryne lemur; giant kingbird Tyrannus cubensis; Cuban crocodile Crocodylus
cubensis).
Table 2 Number of beneficiary species by IUCN threat status and taxonomic order in the 11
OTs. CR = Critically Endangered, EN = Endangered, VU = Vulnerable, NT = Near
Threatened, LC = Least Concern, AR = At Risk.
Taxonomic Order
CR
EN
VU
NT
LC
AR
Seabirds
1
8
7
7
69
0
Land birds
3
3
12
11
31
0
Reptiles
12
9
5
1
0
32
Amphibians
2
2
0
0
0
0
Mammals
0
0
2
0
0
0
OTs Total
18
22
26
19
100
32
Reptiles
Landbirds
Seabirds
Amphibians
Mammals
30
Number of GTS
25
20
15
10
5
0
Figure 2 Number of globally threatened beneficiary species by taxonomic group in the 11
OTs.
St Helena, Ascension and Tristan da Cunha is the Territory with the greatest number of
globally threatened species (total of 15, of which 12 occur in the Tristan group) and the BIOT
is the Territory with the fewest - namely two marine turtle species (see Table 3). It is likely
that the number of globally threatened species occurring in the Caribbean OTs (Anguilla,
British Virgin Islands, Cayman Islands, Montserrat, Turks and Caicos Islands) will increase
as the region’s herpetofauna is formally assessed by the IUCN. All 32 of the At Risk (AR)
reptiles included in this study occur in these five OTs. Montserrat and British Virgin Islands
have the greatest number of Critically Endangered species, with six present in each
Territory. Two of these have apparently been extirpated from islands in the British Virgin
Islands (Anolis roosevelti; Peltophryne lemur).
22
Table 3 Number of globally threatened and endemic terrestrial vertebrates by Territory.
TERRITORY
CR
EN
VU
Total
Anguilla (AIA)
2
3
4
9
Bermuda (BMU)
1
3
0
4
British Indian Ocean Territory (BIOT)
1
1
0
2
British Virgin Islands (BVI)
6
8
0
14
Cayman Islands (CYM)
3
3
2
8
Falkland Islands (FLK)
0
1
4
5
Montserrat (MSR)
6
2
3
11
Pitcairn Islands (PCN)
0
4
5
9
St Helena, Ascension and Tristan da Cunha
3
6
6
15
St Helena (SHN)
1
0
0
1
Ascension (ASC)
0
1
1
2
Tristan da Cunha (TDC)
2
5
5
12
South Georgia and the South Sandwich Islands (SGS)
0
1
4
5
Turks and Caicos Islands (TCI)
3
3
2
8
16
Number of endemic species
14
12
10
8
6
4
2
0
CYM TDC BVI TCI MSR PCN AIA BMU FLK SHN ASC SGS BIOT
Figure 3 Number of endemic terrestrial vertebrates by Territory. St Helena, Ascension and
Tristan da Cunha are listed separately.
In total 66 terrestrial vertebrate species are endemic to individual OTs with the Cayman
Islands having the largest number at 15 (see Figure 3). Of these endemic species all except
three (South Georgia pipit Anthus antarcticus (NT); Tristan thrush Nesocichla eremita (NT);
Falkland steamerduck Tachyeres brachypterus (LC)) are either globally threatened or not
assessed.
Invasive Species in the OTs
In total 85 IAV were recorded across the study OTs. Of these 30 were reptiles, 26 birds, 23
mammals and six amphibians. Thirty-eight IAV species (44.7%) were considered to have
some form of negative impact upon at least one beneficiary species. This percentage varies
23
across invasive group with eighteen invasive mammals (78.3%) considered to be having
some negative impact on beneficiary species compared to only seven invasive bird species
(26.9%) and ten invasive reptile species (32.3%; see Figure 4). A full list of IAV can be seen
in Annex 3.
35
Number of IAV species
30
25
20
15
10
5
0
Reptiles
Birds
Mammals
Amphibians
Figure 4 Total number of invasive alien vertebrate species (blue) and number of invasive
alien vertebrate species impacting upon at least one beneficiary species (red).
The most widespread IAV were rats (Rattus rattus, R. norvegicus, R. exulans) which were
recorded as either Confirmed or Suspected on 473 islands (18.9%) across all of the OTs, in
addition to 66 islands (2.6%) on which they have been extirpated or are subject to an ongoing eradication. At least two of the most damaging IAV classes (Rodents, Predators and
Ungulates) occur in all of the OTs (this may soon change as the reindeer population in South
Georgia is currently subject to an ongoing eradication). The most widespread predator was
the feral cat (Felis catus) occurring on 53 islands (2.1%) across all OTs except SGS and in
TDC. Feral goats (Capra hircus) were the most widespread ungulate species, occurring on
28 islands (1.1%) across six OTs (see Table 4).
Of the other IAV classes, the cane toad (Rhinella marina) was the most widespread
impacting species occuring on 43 islands (1.7%) across six OTs. Other IAV impacting reptile
and amphibian species were restricted to the Caribbean, with the most notable example
being the Cuban treefrog (Osteopilus septentrionalis). Notable impacting bird species
include common myna (Acridotheres tristis), crows (Corvus sp.) and feral chicken (Gallus
domesticus).
24
Table 4 Number of Confirmed or Suspected invasive alien vertebrate species by taxonomic
order per Territory. St Helena, Ascension and Tristan da Cunha listed separately.
TERRITORY
Rodents
Predators
Ungulates
Other
Mammals
Birds
Reptiles
Amphibians
Anguilla
2
3
1
2
2
5
2
Bermuda
3
1
0
0
7
3
1
British Indian
Ocean Terr.
1
1
1
0
7
2
1
British Virgin
Islands
3
3
5
0
5
6
2
Cayman
Islands
3
2
0
1
8
12
2
Falkland
Islands
3
2
4
3
1
0
0
Montserrat
2
1
5
2
3
2
1
Pitcairn
Islands
1
1
1
0
0
6
0
St Helena
3
1
1
1
9
1
1
Ascension
2
0
2
1
5
3
0
Tristan da
Cunha
2
0
3
0
0
0
0
South
Georgia and
the South
Sandwich Is
2
0
0
0
0
0
0
Turks and
Caicos Is
2
2
4
0
1
9
3
Priority Islands
In total, 191 islands were included in the prioritisation as they harboured at least one
beneficiary species and one impacting IAV. All other islands were not included as they either
did not meet this criterion or there was insufficient information available for them. Islands
were initially prioritised for Potential Conservation Value (PCV) only i.e. the maximum
conservation value achievable if all IAV could be successfully eradicated (see table 5).
Islands within 30º of the equator account for 18 of the top 20 islands by PCV. This is
perhaps unsurprising as biodiversity tends to be greater in tropical regions. Montserrat, a
relatively large (> 100km²), tropical island is ranked first due to having a large number of
globally threatened species and not yet assessed reptile species that are either single island
endemics or are restricted to a few islands. This is also true for many of the other large
Caribbean islands such as Anegada, Tortola and the three Cayman Islands. Tristan da
Cunha and Gough lie in the temperate region and lack the threatened and restricted
herpetofauna of the Caribbean islands but are globally important breeding sites for a large
number of seabirds and endemic land birds, many of which are globally threatened.
25
Table 5 Top 25 islands ranked by Potential Conservation Value (PCV) only - this
conservation value can only be realised if all invasive alien vertebrate species are eradicated
from the beneficiary island (practically not feasible at this stage for all islands).
Rank
Island
Territory
1
Montserrat
Montserrat
2
Gough
Saint Helena, Ascension and Tristan da Cunha
3
Cayman Brac
Cayman Islands
4
Anegada
British Virgin Islands
5
Grand Cayman
Cayman Islands
6
Little Cayman
Cayman Islands
7
Saint Helena
Saint Helena, Ascension and Tristan da Cunha
8
Henderson
Pitcairn Islands
9
Tortola
British Virgin Islands
10
Guana Island
British Virgin Islands
11
Little Thatch Island
British Virgin Islands
12
Tristan da Cunha
Saint Helena, Ascension and Tristan da Cunha
13
Norman Island
British Virgin Islands
14
Virgin Gorda
British Virgin Islands
15=
Cotton Cay
Turks and Caicos Islands
15=
Gibb’s Cay
Turks and Caicos Islands
17=
Anguilla
Anguilla
17=
Necker Island
British Virgin Islands
19=
Jost Van Dyke
British Virgin Islands
19=
Grand Turk
Turks and Caicos Islands
21
East Caicos
Turks and Caicos Islands
22
Big Ambergris Cay
Turks and Caicos Islands
23
Pitcairn
Pitcairn Islands
24
Scrub Island
Anguilla
25
South Georgia
South Georgia and the South Sandwich Islands
When filtered for IAV eradication feasibility, 11 islands were considered not to be feasible for
eradication due to either human population size or IAV groups present. Out of the top 20
islands ranked by PCV Grand Cayman, Tortola, and Anguilla all have human populations of
over 10,000. No invasive species group on these islands is considered feasible to eradicate
and they therefore drop out of the prioritisation. Other islands with human populations of
over 1,000 from which rodents, specifically rats, cannot be eradicated drop substantially in
the final (ACV) prioritisation list. These include Cayman Brac, Saint Helena, Virgin Gorda
and Grand Turk.
Table 6 lists the top 25 priority islands when ranked by Actual Conservation Value (ACV)2.
Ten of the 11 OTs included in this study are represented in these top 25 islands, but the list
is dominated by islands from the Turks and Caicos Islands and British Virgin Islands, with
2
The full list of islands ranked by ACV and PCV is available from the RSPB on request.
26
five and nine respectively. This is due primarily to the rich endemic herpetofauna found in
the Caribbean and in these Territories. Further detail on specific islands and key beneficiary
species can be seen in the individual Territory sections. Of the top 20 islands, most have
small permanent human habitation with the largest population being on Jost Van Dyke (297;
2008 Census data).
Island area is currently the biggest determinant of eradication cost, along with complexity
(number of species to be eradicated) and isolation. Estimating costs for individual operations
was not considered constructive at this stage, as these can vary so significantly between
Territories (e.g. from the Falklands where a low-cost ground-based methodology has been
developed and no project has cost more than £20,000 to implement, to Henderson Island
where aerial techniques were used at a cost of c£1.5 million for an eradication attempt in
2011).
27
Table 6 Top 25 islands for invasive alien vertebrate eradication ranked by Actual
Conservation Value (ACV), which incorporates natural reinvasion risk and assumes that only
those IAV for which technically and logistically feasible eradication techniques currently exist
(as of January 2013) are included.
Rank
Island
OT
1
Gough
Saint Helena, Ascension and Tristan da
Cunha
65.58
2
Anegada
British Virgin Islands
38.44
3
Little Cayman
Cayman Islands
28.90
4
Henderson
Pitcairn Islands
43.18
5
Guana
British Virgin Islands
2.93
6=
Tristan da Cunha
Saint Helena, Ascension and Tristan da
Cunha
2.50
6=
Norman
British Virgin Islands
96.16
8=
Cotton Cay
Turks and Caicos
1.08
8=
Necker
British Virgin Islands
0.32
10
Big Ambergris Cay
Turks and Caicos
4.17
11
South Georgia
South Georgia and the South Sandwich
Islands
12 =
Pitcairn
Pitcairn Islands
4.05
12 =
Jost van Dyke
British Virgin Islands
8.52
12 =
Little Ambergris Cay
Turks and Caicos
3.20
15
Salt Cay
Turks and Caicos
6.67
16
New
Falkland Islands
23.63
17
French Cay
Turks and Caicos
0.11
18
Little Tobago
British Virgin Islands
0.25
19
Peter
British Virgin Islands
4.27
20
Ascension
Saint Helena, Ascension and Tristan da
Cunha
97.71
21
Dog
Anguilla
1.96
22
Salt
British Virgin Islands
0.78
23
Montserrat
Montserrat
24
Great Dog
British Virgin Islands
0.36
25
Ile de la Passe
British Indian Ocean Territory
0.21
2
Island Area (km )
3605.42
101.57
28
TERRITORY-SPECIFIC ACCOUNTS
29
ANGUILLA
Top-ranked islands
Island
Key IAV Species
Key Beneficiary Species
Dog Island
Goat
Anguilla bank skink (VU);
Anguilla bank ameiva (AR);
laughing gull (GBP); sooty tern
(GBP); brown booby (GBP);
bridled tern, brown noddy,
magnificent frigatebird, masked
booby, red-billed tropicbird (all
RBP)
Prickly Pear East (PPE) and
Prickly Pear West (PPW)
Black rat
PPE: Anguilla bank ameiva
(AR); laughing gull (GBP); brown
booby, least tern, red-billed
tropicbird (all RBP)
PPW: Laughing gull (GBP);
brown booby, brown pelican,
red-billed tropicbird (all RBP)
GBP = Globally Important Breeding Population
RBP = Regionally Important Breeding Population
Discussion
Management
 The top priority site in Anguilla for invasive vertebrate eradication is Dog Island where
eradication of rats has already been successful. Removing goats from this site could
bring substantial addtional conservation benefits.
 Prickly Pear East and West should be considered as a single management unit when
undertaking a rat eradication due to their close proximity to each other in order to reduce
the risk of natural reinvasion.
 The Anguilla mainland has a number of globally threatened species including the
Endangered Anguilla racer (Alsophis rijgersmaei) and Lesser Antillean iguana (Iguana
30

delicatissima) along with a range of IAV including rats, feral cats and dogs, green iguana
and goats. It is ranked 17th amongst the OT islands for PCV, illustrating its high
biodiversity value. However, due to its high human population, eradication of invasive
vertebrates is not considered feasible at present. Many native species on Anguilla could
benefit from sustained control of feral mammalian predators, goats and green iguana.
Scrub Island, which is ranked 24th for PCV, lies very close to the Anguilla mainland (<
600m) so there is a high risk of natural reinvasion by rats. Because of this, the
eradication of rats from Scrub Island is not currently considered likely to be a
sustainable project.
Research
 The distribution of rats on the islands of Anguilla is general poorly known and further
investigation into their distribution is needed. It would be useful to investigate the geneflow between populations of rats on the mainland of Anguilla and the off-islands – this
could give a good indication as to whether eradication efforts would be sustainable or
whether there would be constant reinvasion. Similar work has been carried out in the
Falkland Islands and has been useful in guiding project selection (S Poncet, pers.
comm.).
 Red cornsnakes (Pantherophis guttatus) have been recorded on Anguilla. A common
pet trade species, the red cornsnake has been identified as potentially having a severe
detrimental impact on native fauna through predation and competition in the US Virgin
Islands and Australia (Platenberg and Boulon 2006; Fisher and Csurhes 2009). They
have also been identified as a significant threat to the endemic subspecies of brownheaded nuthatch (Sitta pusilla insularis) in the Bahamas (Hayes et al. 2004). Studying
the impact of red cornsnake on native fauna in Anguilla, particularly on the Anguilla
racer, would be widely beneficial as little is known about their impacts in the Caribbean
due to their relative recent arrival. Limiting their spread within Anguilla and preventing
their establishment on the other islands should be considered a priority as eradication
would be extremely difficult if not impossible (Fisher and Csurhes 2009).
Biosecurity
 Preventing rats establishing on Sombrero and Little Scrub Island should be considered
a priority due to the presence of two endemic reptile species on Sombrero (Sombrero
ameiva Ameiva corvina and Sombrero dwarf gecko Sphaerodactylus sp.) and one
endemic reptile species on Little Scrub Island (Censky’s ameiva Ameiva corax).
31
BERMUDA
Discussion
 As all of Bermuda’s off-islands lie within 2 kilometres of the mainland where eradication
of IAV is not considered feasible, this study has not identified any priority vertebrate
eradication projects in Bermuda.
 Bermudian conservationists have already successfully restored inshore islands for
conservation (e.g. Nonsuch Island). Constant rat control is required on these islands to
prevent reestablishment. It is likely that the Castle Islands would be a high priority for
this sort of ongoing control.
Research
 Improving knowledge of the distribution of rats (and other IAV) on the smaller islands of
Bermuda would benefit future conservation action.
 The native Near Threatened diamond terrapin (Malaclemys terrapin) is currently found
in only three ponds on Main Island and could most likely benefit from the eradication of
the invasive red-eared slider. Further research is needed on the best approach and
likely benefits.
 Eradication of kiskadees (Pitangus sulphuratus) and American crows (Corvus
brachyrhynchos) is not likely to be feasible at present but control could benefit native
species including the Critically Endangered Bermuda skink (Plestiodon longirostris) and
diamondback terrapin. Further research is needed on the best approach and likely
benefits.
32
BRITISH INDIAN OCEAN TERRITORY
Top-ranked islands
Island
Key IAV Species
Key Beneficiary Species
Ile de la Passe (Peros
Banhos)
Black rat
Hawksbill turtle (CR); green turtle (EN), nesting
seabirds
Ile Yeye
Black rat
Hawksbill turtle (CR); green turtle (EN), nesting
seabirds
Ile Diamant
Black rat
Hawksbill turtle (CR); green turtle (EN)
Black rat
Hawksbill turtle (CR); green turtle (EN)
Eagle Island
Black rat
Hawksbill turtle (CR); green turtle (EN)
Ile Vache Marine
Black rat
Hawksbill turtle (CR); green turtle (EN)
Petite Soeur
Grande Ile Mapou
Ile Pierre
Ile Cipaille
Ile Lubine
Discussion
Management
 Ile Diamant, Grande Ile Mapou, Ile Pierre and Petite Soeur (Peros Banhos) should be
considered as a single management unit if undertaking a rat eradication due to their
close proximity to each other to reduce the risk of natural reinvasion.
 Ile Cipaille and Ile Lubine (Egmont Islands) are effectively connected so should be
treated as a single management unit if undertaking a rat eradication.
 The largest island in the BIOT, Diego Garcia, has significant seabird colonies and
restoration potential. It also has feral cats, donkeys and black rats. Due to the size of the
resident human population, eradication of rats is not currently considered feasible.
33

However implementing sustained control of IAV on Diego Garcia could benefit the
number of important nesting seabird colonies as well as nesting turtles and native forest.
A rat eradication project has recently been undertaken on Ile Vache Marine, led by the
Chagos Conservation Trust (CCT, pers.comm). If this succeeds, there are plans to take
work forward on other, larger islands such as Yeye and Eagle Island.
Biosecurity
 Many islands in the BIOT have no impacting IAV present and biosecurity for these
islands should be given the highest priority.
 Nelson, Sea Cow and Danger Island are all Important Bird Areas and have feral
chickens present which, although unlikely to impact upon breeding seabirds, would
benefit from monitoring.
34
BRITISH VIRGIN ISLANDS
Top-ranked islands
Island
Key IAV Species
Key Beneficiary Species
Anegada
Feral cat; dog; goat; cow;,
sheep; donkey; pig; brown
rat; green iguana; Cuban
treefrog
Anegada ground iguana (CR); Anegada skink (CR);
roseate tern (GBP); leatherback (CR); hawksbill turtle
(CR; green turtle (EN); laughing gull, least tern, royal
tern, sandwich tern, brown pelican (all RBP)
Guana Island
Feral cat; dog; sheep;
Cuban treefrog
Anegada ground iguana (CR); Mona Island boa (EN);
Lesser Virgin Islands skink (EN); hawksbill turtle (CR)
Norman Island
Feral dog; goat; black rat
Anegada ground iguana (CR); Virgin Islands bronze
skink (EN)
Necker Island
Black rat; Cuban treefrog
Anegada ground iguana (CR); Lesser Virgin Island skink
(EN); laughing gull and bridled tern (RBP)
Jost Van Dyke
Feral cat; dog; goat; pig;
small Asian mongoose;
black rat; Cuban treefrog
Mona Island boa (EN); Virgin Islands coqui (EN); yellow
mottled coqui (EN); hawksbill turtle (CR)
Little Tobago
Black rat; goat
Virgin Islands bronze skink (EN); brown booby (RBP)
Peter Island
Green iguana; feral cat;
feral chicken
Virgin Islands bronze skink (EN; hawksbill turtle (CR)
Salt Island
Goat; feral chicken
Lesser Virgin Island skink (EN); Virgin Islands bronze
skink (EN;
Great Dog Island
Black rat, goat
GBP = Globally Important Breeding Population
RBP = Regionally Important Breeding Population
Virgin Islands coqui (EN)
35
Summary
Management
 The highest priority invasive vertebrate eradication project in the BVI at present is on
Anegada (ranked 2nd across all the OT islands) where feral cats and other IAV are
having a severe impact on threatened reptiles and on seabirds. There would need to be
full community support for any project on Anegada as the island has substantial private
ownership.
 Guana Island does not have rodents present, but is a high priority for the eradication of
cats and other feral animals.
 Jost Van Dyke, Little Jost Van Dyke, Green Cay and Sandy Spit would need to be
treated as a single management unit if undertaking a rodent eradication due to their
close proximity to each other to reduce the risk of natural reinvasion.
 Both Tortola and Virgin Gorda ranked very highly for PCV (9 and 14, respectively) but
due to their high human population sizes eradication of most IAV groups is not
considered feasible. Control of small Asian mongoose (Herpestes javanicus) and other
IAV predators on these islands could be highly beneficial for native fauna, especially the
endemic Virgin Islands dwarf gecko (Sphaerodactylus parthenopion; currently
unassessed). Similarly for Little Thatch (ranked 11 for PCV) which, due to its close
proximity to Tortola, is unlikely to represent a sustainable eradication project but again
IAV control could deliver conservation benefits.
Research
 Cuban treefrogs (Osteopilus septentrionalis) occur on many islands in BVI including
Anegada, Guana, Great Camanoe, Necker, Little Thatch and Jost Van Dyke. These
large frogs are voracious predators and have been implicated in declines of native frog
species in the US Virgin Islands and Florida through predation and resource competition
(Platenberg and Boulon 2006; Glorioso et al. 2012). At present, there is no known
eradication method and monitoring their extent of distribution, impact upon native fauna
and removal where possible would be considered highly beneficial.
 Red cornsnakes (Pantherophis guttatus) have been recorded from Tortola and Peter
Island, though these may be waifs and a non-breeding population. A common pet trade
species, the red cornsnake has been identified as potentially having a severe
detrimental impact on native fauna through predation and competition in the US Virgin
Islands and Australia (Platenberg and Boulon 2006; Fisher and Csurhes 2009). They
have also been identified as a significant threat to the endemic subspecies of brownheaded nuthatch (Sitta pusilla insularis) in the Bahamas (Hayes et al. 2004).
Implementing suitable measures to prevent the establishment of red cornsnakes in BVI
would be considered very beneficial as eradication would be extremely difficult if not
impossible (Fisher and Csurhes 2009).
 Surveys to establish a more detailed understanding of the distribution and impacts of
IAV in BVI would be of significant benefit to future conservation actions within the
territory.
Biosecurity
 Rats are not recorded as being present on Guana Island but it lies close to Tortola
(500m). Implementing appropriate biosecurity measures to prevent rats colonising
Guana Island should be a high priority.
 Prevention of rats, mongoose and feral cats establishing on Mosquito Island should be a
high priority, as it is the only predator-free refuge for the Virgin Islands dwarf gecko.
 Mongoose distribution is currently limited to Tortola, Virgin Gorda, Jost Van Dyke, Little
Jost Van Dyke and Beef Island. Preventing the colonisation of other islands should be
considered a priority as mongooses are known to have particularly devastating impacts
on native reptile species (Barun et al. 2011; Hedges and Conn 2012).
36
CAYMAN ISLANDS
Top-ranked island
Island
Key IAV Species
Key Beneficiary Species
Little Cayman
Feral cat; dog; black rat;
green iguana
Sister Islands rock iguana (CR); 5 endemic reptiles;
West Indian whistling duck (VU); red-footed booby
(GBP); green turtle (EN); loggerhead (EN)
GBP = Globally Important Breeding Population
Summary
Management
 Little Cayman is ranked the 3rd most important IAV eradication project in the OTs (ACV)
due to its populations of Sister Islands rock iguana and other endemic reptiles and its
low human population (c. 200 permanent residents). This island is clearly very important
for biodiversity, and exploring the potential for IAV control should be a high priority, as
well as ensuring new IAV do not become established.
 Cayman Brac is ranked 3 for PCV due to its endemic reptile population. For ACV, its
ranking is low due to its large human population which rules out rat eradication. Control
of feral predators could still deliver substantial conservation benefits on the Brac.
 Grand Cayman ranked 5 overall in terms of PCV due in part to the presence of the
Endangered Cayman blue iguana (Cyclura lewisi) and four other endemic reptile
species. Due to the high human population, eradication of IAV is not considered feasible
on Grand Cayman. However, localised control of feral IAV predators could be highly
beneficial to biodiversity.
Research and biosecurity
 Green iguanas (Iguana iguana) are present on all islands (although not yet well
established on Cayman Brac or Little Cayman). They potentially compete with native
Cyclura species though their impacts are not well investigated. Preventing further
establishment of green iguanas on Little Cayman and Cayman Brac should be a high
priority.
37

Red cornsnakes (Pantherophis guttatus) have established populations on Grand
Cayman. A common pet trade species, the red cornsnake has been identified as
potentially having a severe detrimental impact on native fauna through predation and
competition in the US Virgin Islands and Australia (Platenberg and Boulon 2006; Fisher
and Csurhes 2009). They have also been identified as a significant threat to the
endemic subspecies of brown-headed nuthatch (Sitta pusilla insularis) in the Bahamas
(Hayes et al. 2004). Studying the impact of red cornsnake on native fauna in Grand
Cayman would be widely beneficial, as little is known about their impacts in the
Caribbean due to their relative recent arrival. Limiting their spread within Grand Cayman
and preventing their establishment on the Little Cayman and Cayman Brac should be a
high priority as eradication would be extremely difficult if not impossible (Fisher and
Csurhes 2009).
38
FALKLAND ISLANDS
Top-ranked islands
Island
Key IAV Species
Key Beneficiary Species
New Island
Feral cat; black rat;
house mouse; rabbit
Black-browed albatross (EN, GBP); white-chinned
petrel (VU); southern rockhopper penguin (VU);
gentoo penguin (GBP); imperial shag (GBP); thinbilled prion (GBP); seabird IBA
Steeple Jason
House mouse
GBP = Globally Important Breeding Population
Black-browed albatross (EN, GBP); seabird IBA
Discussion
The Falkland Islands have led amongst the Overseas Territories in developing a local
programme of invasive vertebrate eradication projects. These have included attempted
rodent eradications from more than 30 individual islands, as well as projects to remove foxes
from several sites. Unlike many of the other Territories, the majority of land in the Falklands
is in private ownership, including many privately owned islands. Falklands stakeholders have
previously developed their own priority list of islands for future eradications, and the criteria
used incuded owner acceptance and enthusiasm as a key factor. The current project has not
taken this into account, so the resulting list should only be considered along with a local
priority list.
Management
 New Island is ranked 16 for ACV, and would require a multi-species eradication effort. It
has a number of offshore islands in close proximity that would need to be considered
during any eradication attempt.
 Steeple Jason is ranked relatively low for ACV (38) as it only has house mice present
and they are considered to have a much lower impact than either rats or cats on the
Globally Threatened birds considered in this analysis. However, the eradication of mice
from Steeple Jason could remove the main biosecurity threat to the Jason Islands group
where all other islands are rodent-free and important refugia for small seabirds and
39
invertebrates. Mice are known to be having an impact on small birds and invertebrates
on Steeple Jason. This island may therefore carry a higher local priority than apparent
from this exercise.
Research and biosecurity
 Assessment of IAV distribution on West and East Falkland would be very beneficial to
identify isolated IAV populations that are feasible for eradication now, thus limiting their
spread in the future. Rabbits are one species that currently occur in small isolated
populations that could be dealt with before they spread further with potentially damaging
impacts on native vegetation and potential impact on agriculture.
 In general, all islands within 2km of each other should be treated as a single
management unit when undertaking a rodent eradication to reduce the risk of natural
reinvasion. In some circumstances it may be appropriate to “control” rodents on islands,
accepting some level of reinvasion risk. A discussion on the appropriateness of this
approach would need to be held locally.
40
MONTSERRAT
Top-ranked Island
Island
Key IAV Species
Key Beneficiary Species
Montserrat
Feral pig; goat; cow, feral cat;
black rat; cane toad
Montserrat oriole (CR); mountain chicken (CR);
Montserrat galliwasp (CR); Montserrat skink (CR);
forest thrush (VU); leatherback turtle (CR); hawksbill
turtle (CR); green turtle (EN) and 3 other endemic
reptiles
GBP = Globally Important Breeding Population
Discussion



Based on PCV only, Montserrat is the top-ranking island in the OTs. Its ACV ranking
however is significantly lower as its human population size means that rat eradication is
not considered feasible (island size and topography would also make this exceptionally
expensive).
Predator and ungulate control is, within the scales of this assessment, theoretically
feasible. However, given the social conditions on the island (e.g. recreational hunting
being a popular activity amongst some members of the community) and the
inaccessibility of a large part of the island due to ongoing volcanic activity, eradication is
clearly not feasible at present. Control of feral ungulate populations, as is currently being
undertaken in and around the Centre Hills and should be continued as this area is
where most of the key beneficiary species occur. In addition, turtle populations could
benefit significantly from control of pigs on nesting beaches.
Biosecurity should be a high priority for Montserrat, to prevent the establishment of more
IAV species.
41
PITCAIRN ISLANDS
Key Islands
Island
Key IAV Species
Key Beneficiary Species
Henderson
Polynesian rat
Henderson petrel (EN); Henderson crake (VU);
Henderson reed-warbler (VU), Henderson lorikeet (VU);
Henderson fruit-dove (VU); Murphy’s petrel (GBP) Herald
petrel (GBP); Kermadec petrel (GBP); green turtle (EN,
RBP)
Pitcairn
Feral cat; Polynesian
rat; goat
GBP = Globally Important Breeding Population
RBP = Regionally Important Breeding Population
Phoenix petrel (EN); Pitcairn reed-warbler (EN)
Discussion



Henderson Island is ranked 4 across the Overseas Territories for ACV. A second
attempt to eradicate Polynesian rats (Rattus exulans) from Henderson Island should
therefore be a high priority.
Pitcairn Island is ranked 12 for ACV. The eradication of invasive vertebrates on Pitcairn
Island should be considered a high priority. Eradication of feral goats is currently being
planned, and this should have substantial benefits for Pitcairn’s endemic plants.
Biosecurity should be a high priority – this should include preventing new IAV reaching
pest-free Oeno and Ducie Atolls as well as preventing new IAV reaching Henderson
Island and Pitcairn Island.
42
SAINT HELENA, ASCENSION AND TRISTAN DA CUNHA
Inaccessible
Top-ranked Islands
Island
Key IAV Species
Key Beneficiary Species
Gough
House mouse
Tristan albatross (CR); Gough bunting (CR);
Atlantic yellow-nosed albatross (EN); sooty
albatross (EN); Atlantic petrel (EN); Gough
moorhen (VU); 11 other seabird GBPs
Tristan da Cunha
Black rat; house mouse;
cow; sheep
Atlantic yellow-nosed albatross (EN); sooty
albatross (EN); Atlantic petrel (EN); Gough
moorhen (VU); number of potential breeding
seabirds including Tristan albatross (CR)
Ascension
Black rat; house mouse;
rabbit; sheep; common
myna; donkey
GBP = Globally Important Breeding Population
Ascension frigatebird (VU); red-billed tropicbird
(GBP); sooty tern (GBP); black noddy (GBP); green
turtle (EN)
Discussion



Gough Island is the top priority IAV eradication project in the OTs due to the presence of
a large number of globally threatened and globally important breeding seabird species
and two endemic land birds. The high impact of predatory house mice is currently
driving two Critically Endangered species towards extinction, as well as having a
substantial negative impact on breeding seabirds.
Tristan da Cunha is ranked 7 for ACV. The eradication of rodents could benefit both
existing seabird populations and the restoration potential for other seabirds, in particular
the Critically Endangered Tristan albatross (Diomedea dabbenea).
St Helena scored 7 for PCV, solely due to the presence of a single island endemic - the
Critically Endangered St Helena plover (Charadrius sanctaehelenae).However St
Helena is low on the ACV list as the eradication of rats is not considered feasible due to
the human population size. Feral cat control has been shown to be beneficial in semi-
43


desert areas but to have only a marginal impact on pasture land. Control of common
myna (Acridotheres tristis) could also be of potential benefit.
Ascension is ranked 20 for ACV. The eradication of rodents, rabbits and sheep could
enable further seabird recolonisation of Ascension as well as having substantial benefits
for plants and invertebrates.
Implementing appropriate biosecurity measures to prevent rats reaching Gough and the
other uninvaded islands of the Tristan group should be a high priority, as well as
continuing the robust biosecurity measures to prevent the reestablishment of feral cats
on Ascension.
44
SOUTH GEORGIA AND THE SOUTH SANDWICH ISLANDS
Key Islands
Island
South Georgia
Key IAV Species
Brown rat; house
mouse; reindeer
GBP = Globally Important Breeding Population
Key Beneficiary Species
Black-browed albatross (EN); grey-headed albatross
(VU); South Georgia pipit (NT); 20 other seabird GBPs
Discussion



South Georgia ranks highly for both ACV and PCV due to its globally important breeding
seabird populations which include a number of globally threatened species.
Completing the programme of rodent and reindeer eradication that has been started in
South Georgia should be a high priority.
Preventing rodents and other IAV reaching and colonising the rodent-free areas of
South Georgia through the adoption and implementation of robust biosecurity measures
is of the utmost importance.
45
TURKS AND CAICOS ISLANDS
Key Islands
Island
Key IAV Species
Key Beneficiary Species
Cotton Cay
Black rat; goat
Turks Island skink (CR); Potential - Turks and Caicos
rock iguana (CR); hawksbill turtle (CR)
Big Ambergris Cay
Black rat; feral cat;
Cuban treefrog
Turks and Caicos rock iguana (CR); Caicos Island
skink (VU); Caicos gecko (AR); Caicos Island dwarf
boa (AR); Turks Island boa (AR); hawksbill turtle
(CR)
Little Ambergris Cay
Black rat, feral chicken
Turks and Caicos rock iguana (CR); Caicos Island
skink (VU); Caicos gecko (AR); Turks Island boa
(AR); roseate tern (GBP)
Salt Cay
Black rat; feral cat; dog;
cattle, donkeys, mice
Turks and Caicos rock iguana (CR); Underwood’s
dwarf gecko (AR); least tern (GBP)
French Cay
Black rat, mice
Turks and Caicos rock iguana (CR); Caicos gecko
(AR); brown noddy (GBP)
GBP = Globally Important Breeding Population
Discussion
Key islands
 The Turks and Caicos Islands have nine endemic reptile species, many of which have
not been assessed by IUCN and these are the main contributors to the high rankings of
many islands in this Territory. Of particular conservation concern is the Turks Islands
skink (Spondylurus turksae, recommended as Critically Endangered by Hedges and
Conn 2012) which is only known from three islands, but considered extirpated from one
of those (Grand Turk). Eradication of invasive vertebrates and the restoration of Cotton
Cay would be highly beneficial for this species.
 If IAV were eradicated, Cotton Cay could be a suitable site for reintroduction of the
Turks and Caicos rock iguana (Cyclura carinata), which is currently recorded as absent
from the island but was present previously.
46

Due to the close proximity of all of the large Caicos Islands (East Caicos, Middle Caicos,
North Caicos) to each other, to the other Cays (Joe Grant’s Cay, Pine Cay, Dellis Cay,
Little Water Cay) and to Providenciales with a human population of more than 20,000, a
sustainable IAV “eradication” project is not considered feasible on these islands.
However, these islands clearly hold very important biodiversity, and the prospects for
sustained control of key IAV should be explored in order to reduce the risks to endemic
species.
Further research
 The distribution of IAV, especially rats, in the Turks and Caicos is poorly known. Due to
a lack of surveys, rats are only confirmed present on some islands but are strongly
suspected as being present on many others. It would therefore be highly beneficial for
future conservation action to carry out surveys to accurately assess the presence and
distribution of IAV in the Turks and Caicos.
 Red cornsnake (Pantherophis guttatus) is suspected on Grand Turk. A common pet
trade species, the red cornsnake has been identified as potentially having a severe
detrimental impact on native fauna through predation and competition in the US Virgin
Islands and Australia (Platenberg and Boulon 2006; Fisher and Csurhes 2009). They
have also been identified as a significant threat to the endemic subspecies of brownheaded nuthatch (Sitta pusilla insularis) in the Bahamas (Hayes et al. 2004).
Implementing suitable measures to prevent the establishment of red cornsnakes in the
Turks and Caicos would be considered very beneficial as eradication would be
extremely difficult if not impossible (Fisher and Csurhes 2009).
 Cuban treefrogs (Osteopilus septentrionalis) are confirmed on Middle Caicos, North
Caicos, Pine Cay and Parrot Cay and suspected on Big Ambergris Cay. These large
frogs are voracious predators and have been implicated in declines of native frog
species in the US Virgin Islands and Florida through predation and resource competition
(Platenberg and Boulon, 2006; Glorioso et al. 2012). At present, there is no known
eradication method but monitoring their extent of distribution, impact upon native fauna
should be considered.
47
NEXT STEPS
This section outlines some of the key steps, information to collect and points to consider
when proposing to undertake an eradication programme. In addition, the Pacific Invasives
Initiative has produced a user-friendly, practical guide to planning and implementing rodent
and cat eradications. This is a highly recommended resource for those wishing to carry out
eradications in the OTs and a link is provided below.

Social engagement. Having the support of local communities is an essential component
of any eradication programme. Engaging with island owners, communities and other
relevant stakeholder groups and facilitating their participation is essential at all stages of
project implementation from information gathering, to consultation, to decision making,
to eradication work and evaluation (Oppel et al. 2011).

Confirm the presence and extent of an IAV on the island. For some of the priority islands
the presence of IAV (usually rodents) is only suspected due to a lack of recent survey so
confirming whether a particular IAV is present is key. For all islands, establishing the
extent and population size of IAV is vital as this will influence the methodology and cost
of an eradication. Work to establish the connectivity of island rodent populations would
also be useful to determine whether island populations are truly isolated (and therefore
whether eradication is really possible).

Collect information on the status of native species and / or vegetation cover. It is
important to have information on the status of native species that will benefit from the
eradication of IAV and habitat prior to an eradication to provide a baseline against which
operational success can be assessed.

Assess whether there are any non-target species (i.e. not the IAV being eradicated) that
may be affected by the proposed eradication. Some islands will have native species,
livestock or domestic pets that may be affected by an IAV eradication. Such effects may
be accidental poisoning through consumption of bait or by eating poisoned animals or
accidental shooting. A thorough assessment of the risk to non-target species and, if
required, development of a mitigation strategy should be carried out.

Undertake a feasibility study to assess whether eradication is feasible and eradication
methodologies that may be used. This will depend upon various factors including the
type of IAV to be eradicated; size and topography of the island and presence of
susceptible non-target species. A review and assessment of all possible eradication
methodologies should be conducted prior to deciding the most appropriate
methodology.

Programme timeline. A detailed project timeline will aid the effective completion of an
eradication programme. It is important to carry out any eradication at the most
appropriate time of year to avoid severe weather, maximise bait uptake etc. and factor
this into the timeline.

Develop an Operational Plan. Each eradication programme will have its own set of
logistical requirements and constraints. An important factor is the remoteness of the
island to be eradicated. Islands further away from major ports of airports will have a
much higher cost than those closer. Most eradication projects in the OTs will require
external expertise being brought in which will be identified at the methodology
consultation phase. Using local expertise where available and ensuring that local
practitioners receive training during the eradication programme will aid future
eradications.
48

Collect accurate cost information. There are many costs associated with these projects,
and these can vary widely depending on technique, remoteness, non-target issues,
island ownership, livestock, etc. It is important that sufficient resources are secured to
see any project through to completion.

Post-eradication monitoring. This is an essential part of any eradication programme in
order to assess and evaluate the success and effectiveness of the programme. It should
include monitoring for the presence of IAV and of those native species against which
there is a baseline. This should be factored into the programme timeline and costs.

Biosecurity measures. These measures will depend upon an array of factors but are
vital to ensure the long term sustainability of any eradication programme.
Resource Documents
Pacific Invasives Initiative Resource Kit for Rodent and Cat Eradication
http://rce.pacificinvasivesinitiative.org/
There are currently no guides for ungulate eradications but principles outlined here and in
the above document are universally applicable to all proposed eradication projects.
49
ANNEX 1 – Present and Historical Breeding Status full definitions
Parameter
Criteria
Criteria definition
Present
Breeding
Status
Confirmed
Birds, Bats: Confirmed breeding found including evidence: "pairs",
nests, live/dead fledglings, eggs (whole or fragments), adults flying into
crevices or burrows with fish/insects, female with egg in oviduct, Adults
flying with nesting materials in mouth, singing/calling make, bird and/or
pair holding territory, "colony".
Amphibian, Mammal, Reptiles: 1 - Species observed, recorded,
surveyed; or 2 - remains found on the island; reported in a publication
within the last 20 years but no record or survey year is available; or 3 expert confirms on island and has been recorded in last 20 years (no
years or evidence provided).
Probable
Birds, Bats: Breeding not confirmed but is suspected based on a
number of factors and evidence: (BIRDS) breeding adult found in mistnets (female without egg in oviduct), breeding adult fall-outs, radar
surveys, spot-light surveys, acoustic monitoring, guano scents, bones,
used/abandoned nests; expert confirms species but record years
unclear; (BATS) "probable colony"; breeding island mentioned in paper;
species is endemic to the region; species is non-migratory.
Amphibian, Mammal, Reptiles: THIS IS NOT AN OPTION.
Potential
Breeding
Birds, Bats: Species recorded as past breeder but status unclear
(Inconclusive surveys, searches, or data; Inconclusive or no survey but
researcher found suitable breeding; at-sea survey recorded breeders
near a specific island; expert confirms past breeding but does not
provide or know the record/account of evidence type or year of record)
OR species is confirmed/potentially extirpated.
Amphibian, Mammal, Reptiles: Species recorded as past breeder (21 200 years ago) but species is currently extirpated or status unclear.
Most recent survey yielded no evidence of breeding; island or species
has not been surveyed within the last 20 years or unclear if surveyed or
observed; bones from species found on island but undated.
Data
Deficient
Birds, Bats: Island with species recorded as Data Deficient or Potential
Breeding in historic breeding status and status has not been updated in
the past 20 years; not enough data to extrapolate exact island location,
breeding island not provided in data or communication with experts;
data from the last 20 years is not available.
Amphibian, Mammal, Reptiles: Island with species recorded as Data
Deficient or Potential Breeding in historic breeding status and status
has not been updated in the past 20 years; not enough data to
extrapolate exact island location, breeding island not provided in data or
communication with experts; data from the last 20 years is not
available.
Extirpated
Confirmed extirpation from the island.
Non
Breeding
Birds only: Species recorded on island but is known not to breed e.g.
wintering migrants, seabirds or land birds seen flying / foraging only on
island.
50
Historic
Breeding
Status
Confirmed
Birds, Bats: Confirmed breeding found including evidence: "pairs",
nests, live/dead fledglings, eggs (whole or fragments), adults flying into
crevices or burrows with fish/insects, female with egg in oviduct, Adults
flying with nesting materials in mouth, singing/calling make, bird and/or
pair holding territory, "colony".
Amphibian, Mammal, Reptiles: 1- Species observed, recorded,
surveyed; or 2- remains found on the island; reported in a publication
within the last 20 years but no record or survey year is available; or 3 expert confirms on island and has been recorded in last 20 years (no
years or evidence provided).
Probable
Birds, Bats: Breeding not confirmed but is suspected based on a
number of factors and evidence: (BIRDS)breeding adult found in mistnets (female without egg in oviduct), breeding adult fall-outs, radar
surveys, spot-light surveys, acoustic monitoring, guano scents, bones,
used/abandoned nests; expert confirms species but record years
unclear; (BATS) "probable colony"; breeding island mentioned in paper;
species is endemic to the region; species is non-migratory.
Amphibian, Mammal, Reptiles: THIS IS NOT AN OPTION
Potential
Breeding
Birds, Bats: Status unclear. Status unclear (Inconclusive surveys,
searches, or data; Inconclusive or no survey but researcher found
suitable breeding; at-sea survey recorded breeders near a specific
island; expert confirms past breeding but does not provide or know the
record/account of evidence type or year of record) OR species is
confirmed/potentially extirpated.
Amphibian, Mammal, Reptiles: Status unclear (Inconclusive surveys,
searches, or data) or extirpated.
Data
Deficient
Birds, Bats: Island with species recorded as Data deficient, Probable or
Potential Breeding in present breeding status but there is no record or
history on island in the last 21 - 200 years; not enough data to
extrapolate exact island location; data from the last 21 - 200 years is not
available.
Amphibian, Mammal, Reptiles: Species recorded as Data deficient or
Potential Breeding in present breeding status but there is no record or
history on island in the last 21 - 200 years; not enough data to
extrapolate exact island location; data from the last 21 - 200 years is not
available.
NA
All Species: Species listed as Confirmed (native or introduced) for
Present Breeding Status OR was translocated in the last 20 years but is
no longer on the island.
Definitions developed by Island Conservation, BirdLife International and University of
California, Santa Cruz.
51
ANNEX 2 – Full List of Beneficiary Species
Key: AG – Anguilla; AS – Ascension; BM – Bermuda; IO – British Indian Ocean Territory; BV
– British Virgin Islands; CY – Cayman Islands; FK – Falkland Islands; M – Montserrat; P –
Pitcairn Islands; SH – St Helena; SG – South Georgia and the South Sandwich Islands; TR
– Tristan da Cunha; TC – Turks and Caicos Islands
Scientific name
Common name
Acrocephalus taiti
Henderson reed-warbler
Acrocephalus vaughani
Pitcairn reed-warbler
Alsophis manselli
Montserrat racer
Alsophis rijgersmaei
IUCN
status
VU
Taxonomic
group
Land bird
Territory
EN
Land bird
P
AR
Reptile
M
Leeward Island racer
EN
Reptile
AG
Amazona leucocephala
Cuban amazon
NT
Land bird
CY
Ameiva corax
Censky's ameiva
VU
Reptile
AG
Ameiva corvina
Sombrero ameiva
VU
Reptile
AG
Ameiva plei
Anguilla bank ameiva
AR
Reptile
AG
Ameiva pluvianotata
Montserrat ground lizard
AR
Reptile
M
Amphisbaena fenestrata
Cope's worm lizard
AR
Reptile
CY
Anas bahamensis
White-cheeked pintail
LC
Land bird
TC
Anas georgica
Yellow-billed pintail
LC
Land bird
SG
Anolis conspersus
Caymans blue-fanned anole
AR
Reptile
CY
Anolis ernestwilliamsi
Carrot Rock anole
AR
Reptile
BV
Anolis lividus
Montserrat anole
AR
Reptile
M
Anolis luteosignifer
Cayman Brac anole
AR
Reptile
CY
Anolis maynardii
Cayman green anole
AR
Reptile
CY
Anolis pogus
Bearded anole
VU
Reptile
AG
Anolis roosevelti
Roosevelt's giant anole
CR
Reptile
BV
Anous minutus
Black noddy
LC
Seabird
AS, P, SH
Anous stolidus
Brown noddy
LC
Seabird
Anous tenuirostris
Lesser noddy
LC
Seabird
AG, IO, BV, P,
SH, TC, TR
IO
Anthracothorax dominicus
Antillean mango
LC
Land bird
BV
Anthus antarcticus
South Georgia pipit
NT
Land bird
SG
Aptenodytes patagonicus
King penguin
LC
Seabird
FK, SG
Aristelliger hechti
Hecht's Caribbean gecko
AR
Reptile
TC
Atlantisia rogersi
Inaccessible rail
VU
Land bird
TR
Bulweria bulwerii
Bulwer's petrel
LC
Seabird
SH
Calidris fusicollis
White-rumped sandpiper
LC
Land bird
FK
Calidris minutilla
Least sandpiper
LC
Land bird
TC
Calidris pusilla
Semipalmated sandpiper
NT
Land bird
Calliphlox evelynae
Bahama woodstar
LC
Land bird
AG, BM, BV, CY,
M
TC
Caretta caretta
Loggerhead
EN
Reptile
Celestus maculatus
Cayman Island galliwasp
AR
Reptile
BM, BV, CY, M,
TC
CY
Chaetura pelagica
Chimney swift
NT
Land bird
BM, CY
Charadrius melodus
Piping plover
NT
Land bird
BM, BV
Charadrius sanctaehelenae
St Helena plover
CR
Land bird
SH
P
52
Charadrius wilsonia
Wilson's plover
LC
Land bird
TC
Chelonia mydas
Green turtle
EN
Reptile
Chionis albus
Snowy sheathbill
LC
Seabird
AG, AS, BM, IO,
BV, CY, M, P, TC
SG
Chiroderma improvisum
Guadeloupean big-eyed bat
VU
Mammal
M
Chloephaga rubidiceps
Ruddy-headed goose
LC
Land bird
FK
Cinclocerthia ruficauda
Brown trembler
LC
Land bird
M
Cinclodes antarcticus
Tussacbird
LC
Land bird
FK
Crocodylus acutus
American crocodile
VU
Reptile
CY
Crocodylus rhombifer
Cuban crocodile
CR
Reptile
CY
Cubophis caymanus
Grand Cayman racer
AR
Reptile
CY
Cubophis fuscicauda
Cayman Brac racer
AR
Reptile
CY
Cubophis ruttyi
Little Cayman racer
AR
Reptile
CY
Cyclura carinata
Turks and Caicos rock iguana
CR
Reptile
TC
Cyclura lewisi
Grand Cayman blue iguana
EN
Reptile
CY
Cyclura nubila
caymanensis
Cyclura pinguis
Sister Islands rock iguana
CR
Reptile
CY
Anegada rock iguana
CR
Reptile
AG
Daption capense
Cape petrel
LC
Seabird
SG
Dendrocygna arborea
West Indian whistling-duck
VU
Land bird
CY, TC
Dendroica vitellina
Vitelline warbler
NT
Land bird
CY
Dermochelys coriacea
Leatherback
CR
Reptile
AG, M , TC
Diomedea dabbenena
Tristan albatross
CR
Seabird
TR
Diomedea exulans
Wandering albatross
VU
Seabird
SG
Diploglossus montisserrati
Montserrat galliwasp
CR
Reptile
M
Egretta rufescens
Reddish egret
NT
Land bird
CY, M, TC
Elaenia martinica
Caribbean elaenia
LC
Land bird
AG, BV, CY, M
Eleutherodactylus lentus
Yellow-mouthed coqui
EN
Amphibian
BV
Eleutherodactylus schwartzi
Virgin Islands coqui
EN
Amphibian
BV
Epicrates chrysogaster
chrysogaster
Epicrates monensis granti
Turks Island boa
AR
Reptile
TC
Mona Island boa
EN
Reptile
BV
Eretmochelys imbricata
Hawksbill turtle
CR
Reptile
Eudyptes chrysocome
Southern rockhopper penguin
VU
Seabird
AG, IO, BV, CY,
M, TC
FK
Eudyptes chrysolophus
Macaroni penguin
VU
Seabird
FK, SG
Eudyptes moseleyi
Northern rockhopper penguin
EN
Seabird
TR
Eulampis holosericeus
Green-throated carib
LC
Land bird
AG, BV, M
Eulampis jugularis
Purple-throated carib
LC
Land bird
M
Euphonia musica
Antillean euphonia
LC
Land bird
M
Fregata aquila
Ascension frigatebird
VU
Seabird
AS
Fregata ariel
Lesser frigatebird
LC
Seabird
IO, SH
Fregata magnificens
Magnificent frigatebird
LC
Seabird
Fregata minor
Greater frigatebird
LC
Seabird
AG, BV, CY, M,
TC
IO, P, SH
Fregetta grallaria
White-bellied storm-petrel
LC
Seabird
TR
Fregetta tropica
Black-bellied storm-petrel
LC
Seabird
SG
Fulmarus glacialoides
Southern fulmar
LC
Seabird
SG
53
Gallinula nesiotis
Gough moorhen
VU
Land bird
TR
Garrodia nereis
Grey-backed storm-petrel
LC
Seabird
FK
Geotrygon mystacea
Bridled quail-dove
LC
Land bird
BV, M
Grus canadensis
Sandhill crane
LC
Land bird
TC
Gygis alba
White tern
LC
Seabird
AS, P, SH
Halobaena caerulea
Blue petrel
LC
Seabird
SG
Icterus oberi
Montserrat oriole
CR
Land bird
M
Iguana delicatissima
Lesser Antillean iguana
EN
Reptile
AG
Larus atricilla
Laughing gull
LC
Seabird
AG, BV, TC
Larus dominicanus
Kelp gull
LC
Seabird
FK
Larus maculipennis
Brown-hooded gull
LC
Seabird
FK
Leiocephalus
psammodromus
Leptodactylus fallax
Turks and Caicos curlytail
AR
Reptile
TC
Mountain chicken
CR
Amphibian
M
Leucophaeus scoresbii
Dolphin gull
LC
Seabird
FK
Limnodromus griseus
Short-billed dowitcher
LC
Land bird
TC
Loxigilla noctis
Lesser Antillean bullfinch
LC
Land bird
AG, BV, M
Lugensa brevirostris
Kerguelen petrel
LC
Seabird
TR
Mabuya montserratae
Montserrat skink
CR
Reptile
M
Macronectes giganteus
Southern giant petrel
LC
Seabird
FK, SG, TR
Macronectes halli
Northern giant petrel
LC
Seabird
SG
Malaclemys terrapin
Diamondback terrapin
NT
Reptile
BM
Margarops fuscatus
Pearly-eyed thrasher
LC
Land bird
AG, BV, M, TC
Margarops fuscus
Scaly-breasted thrasher
LC
Land bird
M
Melanodera melanodera
White-bridled finch
LC
Land bird
FK
Mimus gundlachii
Bahama mockingbird
LC
Land bird
TC
Myiarchus antillarum
Puerto Rican flycatcher
LC
Land bird
BV
Nesocichla eremita
Tristan thrush
NT
Land bird
TR
Nesospiza acunhae
Inaccessible bunting
VU
Land bird
TR
Nesospiza questi
Nightingale bunting
VU
Land bird
TR
Nesospiza wilkinsi
Wilkin's bunting
EN
Land bird
TR
Numenius tahitiensis
Bristled-thighed curlew
VU
Land bird
P
Oceanites oceanicus
Wilson's storm-petrel
LC
Seabird
SG
Oceanodroma castro
Madeiran storm-petrel
LC
Seabird
AS, SH
Orthorhyncus cristatus
Antillean crested-hummingbird
LC
Land bird
AG, BV, M
Pachyptila belcheri
Thin-billed prion
LC
Seabird
FK
Pachyptila desolata
Antarctic petrel
LC
Seabird
SG
Pachyptila turtur
Fairy prion
LC
Seabird
FK
Pachyptila vittata
Broad-billed prion
LC
Seabird
TR
Pagodroma nivea
Snow petrel
LC
Seabird
SG
Patagioenas leucocephala
White-crowned pigeon
NT
Land bird
AG, BV, CY
Pelagodroma marina
White-faced storm-petrel
LC
Seabird
SH, TR
Pelecanoides georgicus
South Georgia diving-petrel
LC
Seabird
SG
Pelecanoides magellani
Magellan diving-petrel
LC
Seabird
FK
Pelecanoides urinatrix
Common diving Petrel
LC
Seabird
FK, SG, TR
Pelecanus occidentalis
Brown pelican
LC
Seabird
AG, BV, M, TC
54
Peltophryne lemur
Puerto Rican crested toad
CR
Amphibian
BV
Phaethon aethereus
Red-billed tropicbird
LC
Seabird
Phaethon lepturus
White-tailed tropicbird
LC
Seabird
Phaethon rubricauda
Red-tailed tropicbird
LC
Seabird
AG, AS, BV, M,
SH
AS, AG, BM, IO,
BV, CY, TC
IO, P
Phalacrocorax atriceps
Imperial shag
LC
Seabird
FK, SG
Phalacrocorax
magellanicus
Phalcoboenus australis
Rock shag
LC
Seabird
FK
Striated caracara
NT
Land bird
FK
Phoebetria fusca
Sooty albatross
EN
Seabird
TR
Phoebetria palpebrata
Light-mantled albatross
NT
Seabird
SG
Phoenicopterus ruber
American flamingo
LC
Land bird
TC
Plestiodon longirostris
Bermuda skink
CR
Reptile
BM
Pluvialis squatarola
Grey plover
LC
Land bird
TC
Porzana atra
Henderson crake
VU
Land bird
P
Procellaria aequinoctialis
White-chinned petrel
VU
Seabird
FK, SG
Procellaria cinerea
Grey petrel
NT
Seabird
TR
Procellaria conspicillata
Spectacled petrel
VU
Seabird
TR
Procelsterna cerulea
Blue noddy
LC
Seabird
P
Pterodroma alba
Phoenix petrel
EN
Seabird
P
Pterodroma atrata
Henderson petrel
EN
Seabird
P
Pterodroma cahow
Bermuda petrel
EN
Seabird
BM
Pterodroma heraldica
Herald petrel
LC
Seabird
P
Pterodroma incerta
Atlantic petrel
EN
Seabird
TR
Pterodroma macroptera
Great-winged petrel
LC
Seabird
TR
Pterodroma mollis
Soft-plumaged petrel
LC
Seabird
TR
Pterodroma neglecta
Kermadec petrel
LC
Seabird
P
Pterodroma ultima
Murphy's petrel
NT
Seabird
P
Ptilinopus insularis
Henderson fruit-dove
VU
Land bird
P
Puffinus assimilis
Little shearwater
LC
Seabird
TR
Puffinus gravis
Great shearwater
LC
Seabird
FK, TR
Puffinus griseus
Sooty shearwater
NT
Seabird
FK, TR
Puffinus lherminieri
Audubon's shearwater
LC
Seabird
Puffinus nativitatis
Christmas Island shearwater
LC
Seabird
AG, AS, IO, BV,
M, SH, TC
P
Puffinus pacificus
Wedge-tailed shearwater
LC
Seabird
IO
Pygoscelis adeliae
Adelie penguin
NT
Seabird
SG
Pygoscelis antarcticus
Chinstrap penguin
LC
Seabird
SG
Pygoscelis papua
Gentoo penguin
NT
Seabird
FK, SG
Rowettia goughensis
Gough bunting
CR
Land bird
TR
Sphaerodactylus argivus
Cayman Islands dwarf gecko
AR
Reptile
CY
Sphaerodactylus
caicosensis
Sphaerodactylus
parthenopion
Sphaerodactylus sp. 1
Caicos dwarf gecko
AR
Reptile
CY
Virgin Islands dwarf gecko
AR
Reptile
BV
Sombrero dwarf gecko
AR
Reptile
AG
Sphaerodactylus sp. 2
Carval Rock dwarf gecko
AR
Reptile
BV
55
Sphaerodactylus
underwoodi
Spheniscus magellanicus
Underwood's dwarf gecko
Spondylurus anegadae
AR
Reptile
TC
Magellanic penguin
NT
Seabird
FK
Anegada skink
CR
Reptile
BV
Spondylurus caicosae
Caicos Islands skink
VU
Reptile
TC
Spondylurus macleani
Carrot Rock skink
EN
Reptile
BV
Spondylurus powelli
Anguilla Bank skink
AR
Reptile
AG
Spondylurus semitaeniatus
Lesser Virgin Islands skink
EN
Reptile
BV
Spondylurus sloanii
Virgin Islands bronze skink
EN
Reptile
BV
Spondylurus turksae
Turks Islands skink
CR
Reptile
TC
Stercorarius antarcticus
Southern skua
LC
Seabird
TR
Stercorarius lonnbergi
Brown skua
LC
Seabird
FK, SG
Sterna albifrons
Little tern
LC
Seabird
IO
Sterna anaethetus
Bridled tern
LC
Seabird
Sterna antillarum
Least tern
LC
Seabird
Sterna bergii
Great crested tern
LC
Seabird
AG, IO, BV, CY,
TC
AG, BV, CY, M,
TC
IO
Sterna dougallii
Roseate tern
LC
Seabird
AG, IO, BV, TC
Sterna fuscata
Sooty tern
LC
Seabird
Sterna hirundinacea
South American tern
LC
Seabird
AG, AS, IO, BV,
P, SH, TC
FK
Sterna hirundo
Common tern
LC
Seabird
BV, TC
Sterna maxima
Royal tern
LC
Seabird
AG, BV, M, TC
Sterna nilotica
Gull-billed tern
LC
Seabird
BV, TC
Sterna sandvicensis
Sandwich tern
LC
Seabird
AG, BV, TC
Sterna sumatrana
Black-naped tern
LC
Seabird
IO
Sterna vittata
Antarctic tern
LC
Seabird
SG, TR
Sturnira thomasi
Thomas's yellow-shouldered bat
VU
Mammal
M
Sula dactylatra
Masked booby
LC
Seabird
AG, AS, IO, P, SH
Sula leucogaster
Brown booby
LC
Seabird
Sula sula
Red-footed booby
LC
Seabird
Tachyeres brachypterus
Falkland steamerduck
LC
Land bird
AG, AS, IO, BV,
CY, M, SH, TC
AG, AS, IO, BV,
CY, P, SH
FK
Thalassarche
chlororhynchos
Thalassarche chrysostoma
Atlantic yellow-nosed albatross
EN
Seabird
TR
Grey-headed albatross
VU
Seabird
SG
Thalassarche melanophrys
Black-browed albatross
EN
Seabird
FK, SG
Tringa flavipes
Lesser yellowlegs
LC
Land bird
TC
Tringa melanolceuca
Greater yellowlegs
LC
Land bird
TC
Troglodytes cobbi
Cobb's wren
VU
Land bird
FK
Tropidophis caymanensis
Grand Cayman dwarf boa
AR
Reptile
CY
Tropidophis greenwayi
Caicos Islands dwarf boa
AR
Reptile
TC
Tropidophis parkeri
Little Cayman dwarf boa
AR
Reptile
CY
Tropidophis schwartzi
Cayman Brac dwarf boa
AR
Reptile
CY
Tryngites subruficollis
Buff-breasted sandpiper
NT
Land bird
BM
Turdus lherminieri
Forest thrush
VU
Land bird
M
Typhlops catapontus
Erica's worm snake
AR
Reptile
BV
56
Typhlops caymanensis
Grand Cayman blindsnake
AR
Reptile
CY
Typhlops epactius
Cayman Brac blindsnake
AR
Reptile
CY
Typhlops monastus
Montserrat blindsnake
AR
Reptile
M
Typhlops naugus
Virgin Gorda blindsnake
AR
Reptile
BV
Tyrannus cubensis
Giant kingbird
EN
Land bird
TC
Vini stepheni
Henderson lorikeet
VU
Land bird
P
Vireo crassirostris
Thick-billed vireo
LC
Land bird
CY, TC
Vireo magister
Yucatan vireo
LC
Land bird
CY
IUCN rankings from the 2012 Red List
57
ANNEX 3 – Full List of Invasive Alien Vertebrates
Key: AG – Anguilla; AS – Ascension; BM – Bermuda; IO – British Indian Ocean Territory; BV
– British Virgin Islands; CY – Cayman Islands; FK – Falkland Islands; M – Montserrat; P –
Pitcairn Islands; SH – St Helena; SG – South Georgia and the South Sandwich Islands; TR
– Tristan da Cunha; TC – Turks and Caicos Islands
Scientific name
Common name
Territory
Common myna
Taxonomic
Group
Bird
Acridotheres tristis
Aix sponsa
Wood puck
Bird
CY
Alectoris chukar
Chukar partridge
Bird
SH
Amazona ochrocephala
Yellow-crowned parrot
Bird
CY
Anas platyrhynchos
Mallard
Bird
BM, CY
Anolis carolinensis
Green anole
Reptile
AG, CY
Anolis equestris
Knight anole
Reptile
TC
Anolis garmani
Jamaican giant anole
Reptile
CY
Anolis sagrei
Brown anole
Reptile
CY
Anser anser
Goose
Bird
FK
Aratinga erythrogenys
Red-masked parakeet
Bird
CY
Bos taurus
Feral cow
Mammal
BV, FK, M, TC, TR
Bulbucus ibis
Cattle egret
Bird
IO
Cairina moschata
Muschovy duck
Bird
BV
Canis familiaris
Feral dog
Mammal
AG, BV, CY, TC
Capra hircus
Goat
Mammal
AG, BV, FK, M, P, TC
Carlotes versicolor
Bloodsucker
Reptile
IO
Centrochelys sulcata
African spurred tortoise
Reptile
BV
Chlorocebus sabaeus
Green monkey
Mammal
AG
Columba livia
Rock dove
Bird
Corvus brachyrhynchos
American crow
Bird
AG, BM, BV, CY, M,
SH
BM
Corvus splendens
House crow
Bird
IO
Cryptoblepharus
poecilopleurus
Dasyprocta antillensis
Mottled snake-eyed skink
Reptile
P
Saint Lucia agouti
Mammal
M
Dasyprocta punctata
Central American agouti
Mammal
CY
Diadophis punctatus
Southern ringneck snake
Reptile
CY
Didelphis marsupialis
Common opossum
Mammal
M
Eleutherodactylus johnstonei
Lesser Antillean tree frog
Amphibian
AG, BV
Eleutherodactylus planirostris
Greenhouse frog
Amphibian
TC
Emoia cyanura
Copper-tailed skink
Reptile
P
Equus asinus
Donkey
Mammal
Equus caballus
Feral horse
Mammal
AS, IO, BV, M, SH,
TC, TR
TC
Estrilda astrild
Common waxbill
Bird
AS, SH
Felis catus
Feral cat
Mammal
Foudia madagascariensis
Madagascar fody
Bird
AG, BM, IO, BV, CY,
FK, M, P, SH, TC
IO, SH
Francolinus afer
Red-necked francolin
Bird
SH
AS, IO, SH
58
Gallus gallus domesticus
Feral chicken
Bird
Gastrophryne carolinensis
Eastern narrowmouth toad
Amphibian
AG, BM, IO, BV, CY,
M, TC
CY
Gehyra mutilata
Four-clawed gecko
Reptile
P
Geochelone carbonaria
Red-footed tortoise
Reptile
M
Geopelia striata
Zebra dove
Bird
IO, SH
Gonatodes albogularis
Yellow-headed gecko
Reptile
CY
Hemidactylus frenatus
Asian house gecko
Reptile
AS, BM, SH
Hemidactylus mabouia
Afro-American house gecko
Reptile
AG, BV, CY, M, TC
Hemidactylus mercatorius
Coconut-palm gecko
Reptile
AS
Hemidactylus turcicus
Turkish house gecko
Reptile
BM
Hemiphyllodactylus typus
Indopacific tree gecko
Reptile
P
Herpestes javanicus
Small Asian mongoose
Mammal
BV
Iguana iguana
Green iguana
Reptile
AG, BV, CY, TC
Lama guanico
Guanaco
Mammal
FK
Lepidodactylus lugubris
Mourning gecko
Reptile
IO, P
Lepus europaeus
European hare
Mammal
FK
Liolaemus wiegmani
Iguana species
Reptile
AS
Lipinia noctua
Moth skink
Reptile
P
Lycalopex griseus
South American gray fox
Mammal
FK
Mus musculus
House mouse
Mammal
Nesoenas picturata
Madagascar turtle-dove
Bird
AG, AS, BM, BV, CY,
FK, SH, SG, TC, TR
IO
Ophisaurus ventralis
Eastern glass lizard
Reptile
CY
Oryctolagus cuniculus
European rabbit
Mammal
AG, AS, FK, SH
Osteopilus septentrionalis
Cuban treefrog
Amphibian
AG, BV, TC
Ovis aries
Sheep
Mammal
AS, BV, M, SH
Padda oryzivora
Java sparrow
Bird
SH
Pantherophis guttatus
Red cornsnake
Reptile
AG, BV, CY, TC
Passer domesticus
House sparrow
Bird
AS, BM, BV
Phasianus colchicus
Ring-necked pheasant
Bird
SH
Pitangus sulphuratus
Kiskadee
Bird
BM
Pseudemys nelsoni
Florida red-bellied turtle
Reptile
BV
Psittacula krameri
Rose-ringed parakeet
Bird
CY
Ramphotyphlops braminus
Brahminy blindsnake
Reptile
AG, CY, TC
Rangifer tarandus
Reindeer
Mammal
FK, SG
Rattus exulans
Polynesian rat
Mammal
P
Rattus norvegicus
Brown rat
Mammal
Rattus rattus
Black rat
Mammal
Rhinella marina
Cane toad
Amphibian
Serinus flaviventris
Yellow canary
Bird
AG, BM, BV, CY, FK,
M, SH, SG
AG, AS, BM, IO, BV,
CY, FK, M, SH, TC,
TR
AG, BM, IO, CY, M,
TC
AS, SH
Sphaerodactylus mariguanae
Dwarf skink species
Reptile
TC
Stongylopus grayii
Gray's stream frog
Amphibian
SH
Streptopelia decaocto
Eurasian collared-dove
Bird
BV, CY, M
Sturnus vulgaris
Common starling
Bird
BM
59
Sus scrofa
Feral pig
Mammal
BV, M
Sylvilagus floridanus
Mammal
FK
Trachemys decussata
North American cotton-tail
rabbit
North Antillean slider
Reptile
CY
Trachemys scripta elegans
Red-eared slider
Reptile
BM, BV, CY, TC
Trachemys stejnegeri malonei
Inagua slider
Reptile
TC
Varanus exanthematicus
Savannah monitor
Reptile
TC
60
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