Download Welfare of translocated endangered animals in Australia

Welfare of translocated endangered animals in Australia
Ken Richardson
School of Veterinary and Biomedical Sciences, Murdoch University
The Australian fauna has evolved in relative isolation. This has resulted in a biologically
unique and diverse suite of fauna that has been quarantined from many of the
competitors, diseases and predators that have coevolved with fauna on other
continents. With the arrival of Europeans in 1788 the face of the Australian landscape
altered dramatically. Land clearing and degradation as well as associated farming
practices gradually spread across the country. Grazing pressure by domestic stock,
sheep and cattle in particular, spread and increased. Concurrently there was a decline
in native fauna and flora. In many cases the larger macropods, large raptors and other
‘vermin’ were shot or hunted to reduce the perceived predation and competition
between them and the domesticated breeds. This practice went as far as the raising of
bounties on some species such as the Toolache wallaby Macropus greyi and the
Tasmanian tiger Thylacinus cynocephalus. Both are now extinct. Much of the continent
is now threatened by serious ecosystems degradation due to past and in some cases
ongoing mismanagement and neglect. This is mostly due to philosophies that are
primarily exploitative of the landscape rather than one of accommodation and harmony.
Overall the distribution and population number of a great many native vertebrate
species has contracted but a few species, such as the red kangaroo Macropus rufus
and the eastern grey kangaroo Macropus giganteus on mainland Australia, have
increased. The major driving forces that have determined the current populations and
distribution of native vertebrates are massive habitat loss through land clearances,
habitat fragmentation, climate change, hydrological change, soil salinity, fire, and most
significantly, introduced weeds, herbivores and predators.
Australia has the lamentable world record of having the greatest number of fauna
species become extinct in modern times. In Australia since 1788, at least 10 marsupial,
2 bat, 9 rodent, 7 bird and 3 amphibian species have become extinct (Clayton et al,
2006). Furthermore Australia has a large number of vertebrate species that are either
on the edge of extinction or vulnerable to extinction within a short time frame (10-30
years).
So how do we determine how, when and where a vertebrate species is moving towards
extinction? Australia is a signatory to the Treaty for the International Union for the
Conservation of Nature and Natural Resources (IUCN) and as such recognises and
abides by the IUCN’s objective system where the potential risk of a species becoming
extinct within a set time period can be evaluated. In summary this evaluates the
available data for the species (taxon) in question to determine:
•
the level of reduction in population size, over either the last 10 years or three
generations whichever is the larger
•
the geographic range of the species (occurrence and or occupancy)
•
whether the estimated population size of mature individuals is low and declining
•
the probability of extinction within different timeframes.
Most of these criteria have several sub-categories and some of these have further
conditions to further qualify the species in question. Using these criteria, the species
are categorised as being critically endangered, endangered, vulnerable or near
threatened.
Category
Probability of extinction %
Time period
Critically Endangered
50
10yrs or 3 generations
Endangered
20
20 yrs or 5 generations
Vulnerable
10
100yrs
Historically, as part of the conservation of some ‘at risk’ species, small groups of
animals from a founder colony were captured and moved to what was believed to be a
suitable habitat elsewhere. These translocations were an attempt to form new
sustainable colonies to increase the probability of the species surviving if the founder
populations were decimated by a catastrophic event. Following a number of these
translocations, some of which were successful and others not, a wealth of knowledge
and experience was gained. In 2000 this culminated with guidelines being agreed to by
the Australian and New Zealand Environment and Conservation Council FaunaNet on
how, when and where members of ‘at risk’ species may be translocated to other
appropriate habitats. They defined translocations as the movements of living organism
from one area with free release in another. This includes restocking, reintroductions,
and introductions. Restocking is where a number of animals of an ‘at risk’ species are
moved with the intention of either building up the number of individuals in an original
habitat or of introducing greater genetic diversity. Reintroductions are where individuals
of a particular species are released/established into a part of their original native range
from where they had disappeared as a result of human activity or of natural disaster.
Introductions are where individuals of a particular species are released/established
outside of their historically known native range.
Currently there are 2147 species of vertebrate in Australia, comprised of about 216
amphibian, 867 reptile, 741 bird, 2 monotreme, 149 marsupial, and 172 eutherian
species (Clayton et al. 2006). Of these, there are 12 amphibian, 4 reptilian, 8 avian and
6 mammalian species that are critically endangered and 17 amphibian, 10 reptilian, 14
avian and 18 mammalian species that are endangered. Because so little is known
about many of these species, it is probable that many more species are actually ‘at
risk’. Commonwealth legislation requires that management plans are in place for
critically endangered and endangered species to lessen the probability of their
extinction. Many plans have translocations as a critical management tool. Ideally
before any translocations occur, research clarifying the basic biology of the species
especially its reproductive biology and optimal habitat characteristics should be
undertaken. However the situation facing some species is often so bad that time
prevents this happening and the translocations occur under suboptimal conditions.
Hence there can be serious animal welfare implications.
Historically governmental and semi-governmental instrumentalities undertook
translocations. Between 150 and 200 vertebrate reintroductions consisting of about 42
species ‘at risk’ have been undertaken in Australia. In the beginning many were on an
‘ad hoc’ basis and in some cases little is know of the details of the reintroductions, or
whether or not they were successful. In many reintroductions follow up monitoring was
very limited or absent. Gradually substantial relevant data has been gathered and
procedures improved. These have enhanced the probability of successful
translocations.
In recent times non-government organizations such as the Australian Wildlife
Conservancy (AWC) and Birds Australia, have purchased and now manage large
properties so that animal diversity at each site can be maintained ‘in perpetuity’. These
enterprises are ecosystems based and assist the long-term well being of myriads of
species. Such groups, the AWC in particular, are involved with translocations of ‘at risk’
species to suitable habitats on their managed properties. Similarly local interest
groups, such as the Malleefowl Preservation Group Inc. (MPG), have also become
involved in translocations. Groups like the MPG usually operate on a small scale and
represent a specific interest in a single species.
When animals are translocated, stress at some level occurs at all stages of the activity.
Stress is present during an animal’s capture and transport as well as when it is handled
and released. Animals experience a variety of stressors associated with their life in a
new environment. In some cases their genetic make up, as well as disease, can be
stressors. However we have few measures of stress that have been developed for use
with wildlife. To date common sense and experience coupled with the sharing of data
have been the major factors in limiting stress and maximizing animal welfare.
Capture stress
All capture techniques impose some level of stress on the animal involved. Some
simply deprive the animal of liberty for a period of time and may involve minimal stress.
Others can cause varying levels of discomfort and even death. For example when
capturing small mammals, Elliot traps can have a moisture accumulation that dampens
the fur and sometimes causes hypothermia and death. Cage (wire mesh) traps may,
under some environmental conditions, result in hypothermia and exposure. Pitfall traps
can cause fur dampening and thus hypothermia. Occasionally unwelcome
invertebrates such as ants, spiders and centipedes may bite small mammals held in
the same trap. Here the outcomes range from discomfort, to physical injuries and even
death. Even more unusual is that large flies can lay their eggs or larvae directly into the
trapped mammal’s orifices necessitating the euthanasia of the fly-blown animals.
Until recent times medium sized mammals, such as rock wallabies and pademelons,
were captured in wire traps where some animals injured themselves in their attempts to
escape. More recently these traps have been replaced by soft covered traps where
injury is much less likely.
The capture of large mammals such as kangaroos can be difficult. Where animals are
simply chased and caught, skeletal damage (broken bones, joint damage) and
muscular injuries such as capture myopathy may occur, but in practice rarely does.
Capture using chemical darting is usually satisfactory and relatively risk free but
adverse drug reactions and even deaths can occur.
Mist netting of wild birds, under license, is common and widespread in Australia. In the
hands of experienced operators it is a relatively safe technique. Even so adverse
weather conditions, ants and predators may compromise the well-being of captured
birds. Mist nets do require constant vigilance.
Transportation stress
Translocations by their very nature entail transportation of individuals or groups of
animals. Again with many species little is known of how well a particular species will
react to being transported. Here common sense and experience are major factors.
In some cases experience has shown that food and water immediately prior to
transporting is helpful. In other cases it is a hindrance. In a few cases medicating
animals with sedatives has been found to be advantageous. The actual method of
restraining animals during transportation varies with the species. Usually soft cotton
bags are used but with larger animals specially designed cages are necessary.
With some species the time of day is irrelevant but with others it is important. Keeping
the duration of transportation to a minimum is obvious. The prevailing weather
conditions may be important eg., sometimes times it may be too hot or too cold to
move animals. There are periods such as summer when it may be best to avoid
transporting animals totally.
Handling stress
Any handling of an animal entails some degree of stress to that animal. Some species
are more fragile than others. Currently we know little about this. However there are
times of year when any intervention is more stressful than at other times. This could
have a seasonal physiological underpinning. Different handlers impose different levels
of stress onto animals. Some handlers have developed the ‘art’ of handling animals to
a high degree where they cause much less stress than do less experienced handlers.
Release stress
Again this is a poorly known aspect of translocations. The immediate availability of
shelter, food and water are critical for animals being released into a new or novel site.
In some cases animals are released into an environment where supplementation of
food and water and the provision of shelter is undertaken (soft release) for the period of
initial release. In other cases this is not so (hard release). Immediately following
release the prevailing weather conditions play a large part in an animal’s level of
stress. Inclement weather can have serious adverse effects on individuals. The
absence of predators at the time of release is critical but this cannot always be
controlled.
Environmental stress
All the vagaries of the environment can affect released animals, both immediately or in
the long term. The onset of stressful natural events may be slower for example
drought, or rapid such as occurs in large fires or floods. Fire is especially significant as
a stressor of translocated birds. Species such as the noisy scrub bird Atrichornis
clamosus are reliant on small areas of specialized habitat. In the case of the noisy
scrub bird their habitat is dense vegetation in a moderate, reliable rainfall region where
over many years dense leaf litter develops and supports the many invertebrates that
make up their diet. Even occasional fire could destroy either all or nearly all available
habitat within hours or days.
Stressors are insidious in events such as gradual salinisation where habitat is slowly
changing and the landscape gradually loosing biodiversity. Again there is little
knowledge of the level of stress that the animals experience occupying such changing
habitats but common sense tells one that there are serious stressors present especially
for those poorly adapted, either physiologically or morphologically, to the emerging
environment.
In Australia introduced weeds and mammals have had extremely detrimental effects on
many native vertebrates. Introduced pastures, such as mission grass Pennisetum
polystachion and gamba grass Andropogon gayanus, in the Top End, have become
feral and are now significant contributors to the increasing prevalence of late dry
season hot/extremely hot bushfires. These fires are dramatically altering the
biodiversity of the region and ultimately the well-being of numerous vertebrate species,
(Andersen et al 2005). The effects of domestic and feral herbivores have had a
dramatic effect on many translocations. For example competition with feral goats has
placed some colonies of translocated yellow-footed rock wallabies Petrogale
xanthopus at risk. Here the goats simply out-compete native species for available
vegetation and have stripped the areas of forage so that the wallabies slowly starve.
However of all factors involved in mammalian translocations, predation is consistently
the most serious. In Australia, introduced predators such as the European red fox
Vulpes vulpes and the domestic cat Felis catus have been implicated in the demise of
many reintroduction programs. An unfortunate but dramatic example is that of the 14
western barred bandicoots Perameles bougainville reintroduced in 1996 from Dorre
Island off the coast of Western Australia onto the nearby mainland at Heirisson Prong.
The area of the prong had had extensive predator control for many years and there
were believed to be none within the area. The reintroduction was highly successful with
animal numbers building up to about 500 individuals in the winter of 2006. However in
2007 in the interval between one monitoring event and the next, a period of three
months, feral cats entered the protected area and reduced the population to an
undetectable level (Short pers. com., 2008).
Genetic stress
In most instances there are close interactions between environmental stressors such
as nutrition with genetics and disease.
The significance of genetics in translocations is a vexed one. There are opposing
views, with some proponents believing that high genetic variability underpins the
ongoing well-being of translocated animals, and other people disagreeing completely.
Gilbert’s potoroo Potorous gilbertii is Australia’s most critically endangered mammal. It
is found in southern Western Australia and has a total population of about 35
individuals. It has a low genetic variability and there are indications that it is inbred with
lowered male fertility, mismothering and low juvenile survival. How to best improve it’s
long term survival remains a conundrum. Translocations coupled with environmental
management are critically important. Overall the genetic viability of a species is a
sleeper in the debate.
Disease stress
The role of disease as an entity in translocations is little known. From first principles
one can argue that novel diseases could be a serious factor to the well being of any
translocated animal. In some instances translocation authorities are unwilling to
translocate animals harbouring disease (Mathews et al., 2006). An example is the
population of western barred bandicoots Perameles bougainville that has been found
recently to have the debilitating condition of papillomatosis carcinomatosis virus
(Woolford et al., 2008).
Another example is the fate of the brush-tailed bettong Bettongia penicillata in Western
Australia in recent times. Following many reintroductions coupled with a broad-scale
fox control program in the late twentieth century dozens of successfully sustainable
colonies were established. However over the past decade the brush-tailed bettong has
undergone substantial and rapid declines that have particularly affected the natural
remnant populations and the largest of the reintroduced populations.
Extensive research points to two possibilities. The first is that the animals in the
colonies have been under environmental stress and that climatic changes over the past
decade have made them less viable. Another view is that a blood borne trypanosome
parasite infects many of the translocated bettong colonies. It is possible that these
parasites lower the ‘fitness’ of infected animals and that this increases the probability of
them being predated.
Usually stressors such as capture, handling, transportation and release are of low
significance in the success of translocations. Operator common sense and
experience, coupled with attention to each animal’s welfare, have limited the immediate
stresses of translocations, although this has not been quantified. The main causes of
translocation failure with mammals are predation and/or environmental factors at the
release site. Being predated is the ultimate stress that an animal can be subjected to.
The vagaries of environmental influences also stress individuals and populations, but
again there has been little quantitative assessment of these risk factors to date.
Starvation, water deprivation and a lack of available high quality resting sites are
significant natural stressors but generally there is little that we can do about them.
Case studies of current problem areas involving translocations of animals
in the wild.
1. Crocodilians
By 1970 hunting had reduced the Australian saltwater crocodile Crocodylus porosus
population to about 5,000 individuals. Following the cessation of hunting in 1971 the
population has slowly risen to its current level of about 80,000 individuals. As the
crocodilian population has aged, more and more animals are reaching sizes where
they are dangerous to humans. In northern Australia the use of riverine and coastal
environments by humans and saltwater crocodiles results in the need to relocate
threatening crocodiles. Capture alone can cause significant stress to large crocodilians
due to lactate build up. Prevailing hot conditions, confinement by roping animals to a
flat bed base and subsequent transportation, in some instances many hundreds of
kilometres, stresses animals. In some instances very large crocodilians (>4m) die
following translocation. However because of their danger to humans these relocations
will continue. There is a great need to determine how we do relocations better.
2. Rehabilitated animals
Many injured animals appear to recover well when cared for by volunteer groups such
as the Australia Zoo, Wildlife Warriors and Wildlife Information Rescue and Education
Service. However even if these individuals are released back into the same area from
which they originally came from, their original niche is most likely occupied and is no
longer available. Consequently these released animals come into conflict with
conspecifics and are highly likely to be predated. Most validated scientific studies
indicate a high (upto 100%) mortality in released animals. There are obvious questions
of animal welfare associated with wildlife rehabilitation.
3. Conflict between habitat use by industry and a species ‘at risk’.
There is no doubt that land clearance results in the death of a large proportion of the
animals that are displaced. Recently where land clearances are planned for human
habitation the developers relocate the resident populations of ‘high profile’ vertebrates
such as bandicoots, koalas and kangaroos. However little consideration is given to the
other animal and plant entities in the ecosystem about to be destroyed.
In a growing number of cases problems arise with where the ‘high profile’ animals are
to be relocated. In some instances even a small number of animals cannot be readily
relocated. There may simply be no optimal site to relocated the entire population.
There may be optimal habitat present that is already occupied by conspecifics.
Consequently the decision of what is the best option can be difficult. In the first case if
one moves the entire group to a suboptimal but unoccupied, site the group as a whole
may not flourish. In the second case, small groups of 2 to 4 animals can be introduced
into a number of established colonies. The problem here is one of whether or not
individuals will be accepted into the extant colony. There are many factors determining
the acceptance or otherwise of an individual by the colony. In some instances
intraspecific fighting can be extensive and injure animals involved. In the worst case
individuals die.
Overall translocations are being used to manage more and more ‘at risk’ species. The
current procedures being used have been fine-tuned over time and result in more and
more successful outcomes. The stresses to the individuals involved have not been
evaluated but to do so could in itself compromise the welfare of those animals. There is
a need for research into how best to reduce stress during relocations but the
opportunities are limited.
Acknowledgements
I would like to thank Dr J Short for his advice and earlier discussions on the topic. I
would also like to thank Drs A Bradley, P Clark and P Spencer who have each made
useful comments on the content of this paper.
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