Download Ile Aux Aigrettes Nature Reserve, Mauritius

Ile Aux Aigrettes Nature Reserve, Mauritius
Ile Aux Aigrettes is a small island in the Indian
Ocean, situated in the Mahebourg Bay lagoon off
the southeastern coast of the mainland island of
Mauritius. (Approx 20.17S, 57.33E).
Human disturbances, logging, and the
introduction of alien species have contributed to
the degradation of the island habitats.
Ile aux Aigrettes
©Roger de la Harpe (www.africaimagery.com)
The 26 hectares of the Ile Aux Aigrettes were
declared a Nature Reserve in 1965.
Ecosystem type
Ile aux Aigrettes constitutes a refuge for the critically
endangered endemic species of ebony (Diospyros
egrettarum), and Bois de Boeuf (Gastonia mauritiana), the
endangered Bois de Chandelle (Dracaena concinna), the rare
Bois de Fer (Sideroxylon boutonianum), and candle wood
and a species of orchid Oeniella aphrodite.
Endemic animals include the Mauritius Pink Pigeon and
the Ornate Day Gecko. There are approximately 700 species
of native flowering plants on the archipelago, of which 311
are endemic.
The island vegetation is mainly composed of coastal ebony
forest and strand scrub flora.
Ornate Day Gecko ©Roger de la Harpe
(www.africaimagery.com)
Problems/threats
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Native species are under intense pressure from introduced plant and animal species.
There are 97 known introduced plant species on the island, 28 are considered major weeds, including
false acacia (Leucaena leucocephala), prune malgache (Flacourtia indica) and tecoma (Tabebuia
pallida). Others such as Asparagus setaceous and Kalanchoe pinnata are not currently present at high
densities but represent a potential threat.
Rats, cats, mongooses, goats and chickens were previously present on the island, but have been
successfully eradicated, mostly through trapping. Rats have been poisoned.
There are still a number of alien animal species present on the island, these include shrews, Giant
African landsnails (Acatina spp.), Indian wolfsnake (Lycodon aulicus) and agamid lizard (Calotes
versicolor). Several species of house geckos are also present on the island. These species impact
native species in several ways. They affect native invertebrate and reptile species both as competitors
and predators; they feed on native fruit, seedlings and birds' eggs.
Aims of the project
The first aim of this project is to
conserve and re-establish the native plant
and animal species.
The second aim is to develop a model for
restoration that can be applied to other
sites.
Interior of Ebony (Diopsyros egrettarum) forest
©Roger de la Harpe (www.africaimagery.com)
Description of project activities
In 1984 The Mauritian Wildlife Foundation established a watchman on the island to prevent illegal
woodcutting. Restoration work on Ile Aux Aigrettes has been carried out by the Foundation since
1985.
Eradication of alien species
Weeding programmes were established in 1985,
with the sugar cane industry providing labour for
certain periods of the year. Physical techniques are
generally used to remove weeds, although
chemicals are sometimes used for maintenance
weeding, as it is much more time-efficient.
An experimental method of weed management
using the Aldabran tortoise is currently being
tested.
Aldabran tortoise © Frankie Hobro
Based on advice from experts from New
Zealand, anti-coagulant poisons were used to
kill rats without affecting native species. Cats
and mongooses were removed by trapping.
Removal of weeds © Dr John Mauremootoo
No efforts have yet been made to eradicate the
Giant African landsnails (Acatina spp.) or the
Indian wolfsnake (Lycodon aulicus), although
the populations have been surveyed. Future
eradication programs will look to previous
successes such as the work of Simberloff in
Florida, published in 1997. The Indian
wolfsnake is found at very low densities on
the island. Nic Cole, a herpetologist currently working on the island, has found only one wolfsnake
for every 120 hours of intensive research.
Researchers on the island feel that, given current technology, there is little hope of eradicating either
agamid lizard (Calotes versicolor) or house geckos. Nic Cole is currently investigating the
interactions between the native and introduced geckos on the island. Fortunately, he is finding that
there are relatively more native geckos in restored vegetation than in invaded communities. Agamid
lizards are much more common in the open areas that are newly weeded and appear to decrease once
the vegetation cover increases.
Managers of the island have yet to find a completely effective bait that attracts House Shrews to live
traps or for poisoning. Poisoning has proved problematic as an effective poison has not yet been
found. Although live trapping using a ‘rolling front’ across the island has been largely effective, there
are fears that viable populations remain. The managers are looking into new baits, possibly using
micro-encapsulated shrew scent, and considering the use of dogs that can find ‘trap-shy’ individuals.
Planting
Weeding activities are followed by the establishment of pioneer species.
The island is divided into 12.5x12.5m grids for management purposes, each grid is surveyed and
given a planting prescription, which can range from no planting to full planting.
Seedlings are planted to assist natural regeneration. In some areas, enrichment planting of climax
species is also necessary.
20 endangered endemic plant species have been introduced to the island since restoration work began.
The Mauritian Wildlife Foundation is aiming to plant 19 endangered species on the island in the near
future.
Reintroductions
Over 30 Mauritius Kestrels were reintroduced
between 1990 and 1994, 35 pink pigeons were
reintroduced in 1994.
A range of indigenous reptile species will be
reintroduced once the conditions are suitable, in
particular when shrew populations have been
eradicated.
A habitat requirement study will be carried out
before endangered native passerine populations,
including the Mauritius fody, are released on
the island. The success of the release also relies
on the eradication of shrews.
Mauritius pink pigeon ©Roger de la Harpe
(www.africaimagery.com)
Associated activities
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Nursery
A nursery on the island provides
thousands of endemic plants per
year to be replanted.
Seeds are collected on the islet
and from some defined areas on
the mainland. Where possible,
efforts are made not to mix
mainland populations as they may
have separate genotypes.
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Ecotourism
MWF provides guided tours of
the islet. In this way people can
witness an ecosystem which is
very similar to that prior to
human settlement.
The development of ecotourism
facilities was funded by the
Government of Mauritius and
other donors including the
Japanese Expo Fund.
Environmental
Education
The ecotour provides
educational opportunities,
though it is not its main aim.
Ad hoc school visits and
volunteer activities are
organised on the islet.
However there is no specific
education programme for the
Islet.
Results
The eradication of rats was successfully
achieved in 1991. Shrew eradication is an ongoing effort.
To date, 86% of the island has been weeded at
least once. This operation should be complete
within the next three years. Intense weeding
efforts will be maintained until 2010 and will
gradually be reduced as the forest canopy is
restored. Under a good canopy, an area will
require weeding once every five years.
In 2000, the island’s population of pink pigeons
exceeded 80 individuals. The reintroduction
was successful, however the birds are
susceptible to diseases from introduced birds
and need supplementary food.
Candle tree (Dracaena concina)
©Roger de la Harpe (www.africaimagery.com)
The Aldabran tortoises do show a grazing preference for introduced species and are helping to control
weeds.
Lessons learned
The removal of plant and animal alien species is
necessary before planting activities can begin.
Natural regeneration of native species will occur
once alien species have been removed, provided the
seed bank is sufficient.
Re-weeding has to be timed correctly in order to
optimise results. From 1997-99, maintenance
weeding was insufficient due to a shortage of staff,
wasting most of the initial work. The development
Burning of weed vegetation © Dr John Mauremootoo
of chemical and biological techniques should reduce the human labour required, however the
latter is still at an experimental stage. Initially, the exotic woody materials were piled up and
left to rot. It was later found that these piles helped weed regeneration and the material is now
burned.
Both trapping and poison techniques have failed to eradicate shrew populations. A
combination of both techniques is being tested.
Finally, the lessons learned from this project have been applied to restoration work in
Rodrigues and on Round Island.
Stakeholders
The main stakeholders are the local people and the Government of Mauritius, which leases
the island to the Mauritian Wildlife Foundation. Initially the development of the project
resulted in the loss of earnings from woodcutting for the local Mahebourg people. However
this almost coincided with the introduction of gas as an energy source which reduced the
losses. Since then restoration and ecotourism activities have created employment
opportunities for the local communities.
For more information, please click on the links below.
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http://www.mauritian-wildlife.org/ile.htm
http://pages.intnet.mu/nathraj/article2.html
Other restoration projects in Mauritius
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Upland conservation management areas
Anse Quitor Nature Reserve on Ile Rodrigues
Grande Montagne Nature Reserve on Ile Rodrigues
Community restoration plots in Rodrigues
Round Island
Mondrain Nature Reserve
Reference
Varnham, K.J., Roy, S.S., Seymore, A., Mauremootoo, J.R., Jones, C.G. &
Harris, S. (2002). Eradicating Indian musk shrews (Suncus murinus,
Soricidae) from Mauritian offshore islands. In: C.R. Veitch & M.N. Clout
(eds.). Turning the tide: The Eradication of Invasives Species, pp. 342-349.
IUCN SSC Invasive Species Specialist Group. IUCN, Gland, Switzerland and
Cambridge, UK.