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Ile aux aigrette
1. PRACTICAL REPORT
TITLE: ILE AUX AIGRETTE NATURE
RESERVE(FAUNA & FLORA OF PAST AND
PRESENT)
BIOL 1008(Y1) MASCARENE NATURAL HISTORY
DATED: 05/02/16
2. Table of content
Introduction...........................................................................................................................1
-Location of the island
-History of the island
The islet's native flora and fauna, past extinction and current situation regarding
Mauritius biodiversity..............................................................................................................1-2
-Why is Ile aux Aigrettes has been chosen for conservation
Flora of Ile aux Aigrettes............................................................................................................2-3
-Description of the forest
-Invasive alien species impact, control and eradication
-Seed banks and natural seedling
Fauna of Ile aux Aigrettes............................................................................................................4
-Description of the fauna
-Reintroduction of species
-Conservation of the species
Re-introduction, translocation and use of analogue species as conservation
tools..............................................................................................................................................3-4
Species and habitat approaches to conservation of Mauritian
biodiversity……………………………………………………………………………………..5
-Marine Influence
3. Ile aux Aigrette
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INTRODUCTION
Location
Ile aux Aigrettes is situated in Mahebourg Bay,about 800m off the southern coast of Mauritius.
Ile aux Aigrettes is a coralline limestone islet, of about 27hectars, made up of calcareous remains of
marine life. The island is not made up of basaltic rocks and it is about 13m above sea level at its
highest point. However the topsoil of the island is not more than 15cm deep.
History of the Island
In the 1600's the island was occupied by the Egret bird, which is a white fishing bird with long legs.
Therefore Ile aux Aigrettes got it name from these birds but now the Egret no longer come on the
island
During the Second World War, the tiny islet was used by the British as a military base. Canon and
some buildings can still be seen. However they clear most of the native forest as the ebony trees that
was found there was a hard wood, ideal for making furniture and boat
After the war Ile aux Aigrettes was used as a private land for breeding of goats.
Finally, in 1965 Ile aux Aigrettes became a Nature Reserve and conservation programs then started.
The Mauritian Wildlife Foundation launched their project of restoring the original fauna and flora of
the island. So endangered species were brought there in order to be saved. They also offer the public
the chance of visiting the island so that everyone can enjoy the nature and be aware of conservation
done on Ile aux Aigrettes.
The islet's native flora and fauna, past extinction and current situation regarding Mauritius
biodiversity
The fauna and flora of Ile aux Aigrette is very different from that of the mainland of Mauritius.
In fact, what came first, the fauna or the flora?
It is actually a controversial topic since we still have no answer for it, just like the chicken-egg
theory. Nevertheless when we talk about an island, what is of our concern is the conservation of its
fauna and flora.
Why Ile aux Aigrettes has been chosen for conservation?
The main reason why Ile aux Aigrettes was chosen for conservation is due to its isolation. As it is
separated from the mainland, eradication and control of predators such as rats, can be performed.
The isolation of the island therefore allows a control in the biodiversity but also favour re-
introduction of native species. Ile aux Aigrettes is also one of the rarest place that have not be
ecologically destroyed by agriculture.
The island location and accessibility is another reason why Ile aux Aigrettes is ideal for the
4. Ile aux Aigrette
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conservation project. The island is not as steep, rocky and inaccessible as compare to the Black
River Gorges or mountains such as Trois mamelles and Le Corps de Guard
Flora of Ile aux Aigrettes
Description of the forest
The island is made up of a dry coastal forest and most of the trees are native but there are still some
exotic plants around the islet, such as Cryptomeria.
As the island is made up of corals, the canopy is shorter than the mainland, Mauritius.
Around the island, we can find a clear native forest (fig 1.0) and we can also note that the soil is
white or pale brown. This part of the forest is less dense due to the origin of the island, but also
because deforestation has occurred. The Latenier Bleue which has been re-introduced are mainly
found near the coast as well as smaller Ebony trees. No big black Ebony tree can be found around
the coast.
At the centre, there is a denser, humid forest with a darker soil due to organic matter.
Moreover an abundance of ferns, humus and mosses can be observed in the humid condition.
As the roots can go in deeper soil, the trees at the centre are taller and it is made up of Ebony, Bois
de Chandelle or Bois Boeuf. Native Orchid, such as the Angreacum Orchid can still be found on
some of the trees.
Invasive alien species impact, control and eradication
Since 1984, the Mauritian Wildlife Foundation began the restoration programs on Ile aux Aigrettes.
They has eradicated most of the invasive species such as the exotic plants and animals and planted
native ones. Now cat, dogs, mongooses, chicken and goat have also been remove from the island so
that the native species can survive. Weeds such as the acacia , the prune malgache and the tecoma
have also be removed and native species such as the Dodonaea viscosa, Gastonia mauritiana,
Pandanus vandermeeschii, Tarenna borbonica and the Dracaena concinna was planted to replace the
invasive species. The eradication of invasive species thus prevents any disturbance by the exotic
species and thus a heterogeneous environment can also be maintained.
One of the plant mentioned above, known as the tambalacoque(sideroxylon grandiflorum), is now
extinct. There is also the latanier (fig 2.0) which is specifically adapted to the animals that are
indigenous. It was extinct but now it has been re-introduced from Ile Ronde.
There are many reasons for the extinction of this plants amongst which are: Deforestation for
agriculture and settlement. This huge decline in Tambalacoque has led to a cascade extinction
especially for the Dodo(Raphus cucullatus) since they used to coexist.
Moreover the Latanier became extinct from Ile aux aigrette due to many reasons amongst which are:
Presence of rats which literally stops regeneration by consuming the seeds of plants.
They are late successional species just like the Ebony, as a result they were overcome by
successive plants.
This is because different species are adapted to different growing times and requirements.
Ebony (fig 3.0) is a late successional species due to its adaptation for growth and its special fruiting
season, as we have noticed on the island. It grows in the middle of the forest in the moist soil.
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Among so many species we also have the keystone species, for example the figs.
As noticed: it grows high up on trees and germinates straight up although they are rooted to the
ground and also accumulate humus. The fig trees are an important fruit resource due to their non-
specific flowering seasons.
Moreover there is the Bois De Fer which is 170 years old but only present in small numbers as only
one of the five adult trees is left.
The table below shows the plant species that can be found on Ile aux Aigrettes.
Plant species on the island Bois qui vit (Endemic)
Latanier Bleue(Endemic) Angreacum orchid(Native)
Ebony tree(Endemic) Ficus reflexa-figs(Keystone )
Bois de Boeuf(Endemic) Trochettia boutoniana(Endemic)
Bois de Chandelle(Endemic) Bois d’olive(Endemic)
Bois clou(Endemic) Tambalacoque (Extinct)
Seed banks on the island (fig 4.0)
Presence of seed banks on the island allows the conservationist to learn on the germination process
and history of the plant before planting it or by allowing the formation of natural seedling.
Natural seedling
If the seeds are planted and favourable conditions are provided by people, the plant will be weak
and may not resist unfavourable conditions. But if they are allowed to disseminate by the different
vectors and encounter unfavourable conditions during their first season of growth, the plant
becomes stronger and is sure to resist bad weathers in the future. And this is greatly helped by the
Aldabra tortoises(fig5.0).
The table below show a list of some species, in the form of grains or seedling, which are found in
the nursery.
Plant species in the nursery Trochetia boutanianum
Dodonea vidcosa Premna serratifolia
Diospyros egrattum (Ebony tree) Oatorit lodgessi
Clerodendron helepo Oeniella Aphrodite (orchid)
Fauna of Ile aux Aigrettes
Description of the fauna
Ile aux Aigrettes is made up of a unique biodiversity, indeed its fauna. While walking on the island,
we might through that guava tree or the eucalyptus tree is present but it is another native tree, the
Bois de loup, which is morphologically similar; it is called analogous species. Some of the plants of
the island are dioecious, the male plant is different from the female one. An example is the ti clou
and barcou.
Some species nearly became extinct but due to the restoration they have increased in numbers and
no more endangered but still need to be protected. They are as follows:
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Pink pigeon
Mauritius fody
Olive white eye
Gecko
Telfair skink
The giant Aldabran tortoises can be found on the island as the two native species of Mauritius are
now extinct. The Mauritius Tortoises were known as the dome-shape tortoises(Fig 6.0) and the
sadle-shaped tortoises (Fig 7.0).
The Mauritius Fruit Bat (Pteropus niger) can also be found on Ile aux Aigrettes. (Fig 8.0)
In order for conservation to be done on the island, predators have been eradicated, but there are still
some exotic species that affect the native ones. As example , we can still find on the island shrews,
the Giant African landsnails, the Indian wolfsnakear the agamid lizard that compete with the native
species .These aliens species feed on native seedlings and fruits as well on bird's eggs. They also
affect native invertebrates and reptile species such as the Telfair Skink, as they act as both predators
and competitors.
Re-introduction, translocation and use of analogue species as conservation tools
After a successful eradication of alien species, now native animals could be introduced, re-
introduced and translocated on the Island. The Mauritius Kestrels(Falco punctatus), the Pink
Pigeons, the Mauritius Fody(Faudia rubra), the Olive White-eyes(Zosterops chloronothos) , the
Telfair's skinks( Leiolopisma telairii) and the Giant Aldabran Tortoises were brought to Ile aux
Aigrettes.
We have reintroduction of prime species such as: the Gueko(fig 9.0)and the Telfair skink(10.0) as
ile aux aigrette is the best place for conservation.
Furthermore the conservation process regarding the birds is successful as well. For example the,
Mauritius fody(Foudia rubra )(11.0): chicken and eggs were rescued and looked after and 90
birds were released on the island. They were watched over closely and what they noticed was that
they formed pairs and started to breed. Even if they increased in numbers, they still need to be
protected as they are critically endangered as they are found only in Mauritius. They can be
indentified by their distinguished colours, for example the mae have a bright red head in the
breeding season. They feed on insects, fruits, nectar, seeds and eggs
Olive white eye(zosterops chloronothos)(fig 12.0): when these were found they were in small
numbers. They were rescued and moved to ile aux aigrette. They were watched to make sure that
they settled on the island. They were identified due to the small chips inserted in their legs and their
beautiful olive colour. They are also critically endangered as they are found only in Mauritius, they
feed on insects and nectar and lay up to 5 pale green eggs.
Pink pigeon (Nesoenas mayeri)(fig 13.0): these are endemic to Mauritius and in 1990 only 9 were
left in the wild. So they were rescued and moved to ile aux aigrette where they are monitored
closely and provided with favourable conditions to prevent it from becoming extinct. They feed on
buds, leaves, flowers, fruits and seeds and usually lay 2 white eggs in nest of twigs.
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Aldabra tortoises(Geochelone gigantean)(fig 5.0) : they are about 20 roaming on the island
which are a wild breeding group. They feed on leaves on fruits of plants and know how to
distinguish between the right one due to their fussy character. These are quite vulnerable since they
are in small numbers and are native only to Seychelles and Aldabra. The males are bigger than the
females and they feed mainly on plants. They usually lay an average of 25 eggs. These tortoises
have been brought to the island in order to stimulate the role of the extinct Mauritius Tortoises by
disseminating the seeds especially Ebony ones.
The Fruit bat( which the government are trying to cull)(fig 8.0) is the last species of bat left on the
island but monitored closely on Ile aux aigrette since they are endangered as they are quite
vulnerable to extinction. These fruit bats are also considered as a keystone species as they play an
importance role in the dissemination of seed.
To preserve the bats, laws are being applied, however due to political issues the matter is now a
controversial one.
Telfair's shrink: this species has been successfully translocated from Ile Ronde to Ile aux Aigrettes
and in 2006, 250 species have been recorded even if their population were slowing down when rats
ate their eggs. To solve that problem small ones are kept in special nusery until they become big
enough to survive and find their food by themselves. Moreover they were bred in captive so as to
increase them in numbers and then later release them in a favourable habitat.
For plants, there are two main way of propagation of plant on Ile aux Aigrettes, namely cutting and
seedling. But air- layering is another way of propagation also used on the island. Cutting: Stems are
usually cut into a section where the nodes are present the root is then allow to grow in the soil.
Seedling: This method of propagation is done in the nursery, where seeds are allowed to grow and
later planted on the island. Air-layering: Air layering is like cutting but the chosen stem is clear, that
is, the bark is peel off, then it is attached with aluminium foil containing moss and no air can enter.
The roots are allowed to grow on the plant and later are cut off from the main one to be planted as a
new plant. This is also known as cloning. On ile aux Aigrettes, some plants are propagated by air-
layering.
Species and habitat approaches to conservation of Mauritian biodiversity
Marine Influence
The sea greatly influences the biota of an island. This also applies to the former islet ile aux aigrette
as it contains a unique type of coastal vegetation that used to be found in the coastal lowlands of
Mauritius. As we have observed the salinity acts as a gradient that influences the growth of the
different plant species present on the island. For example, the palms that have been reintroduced
from Round Island are seen to grow better on the coastal areas. Therefore concluding that different
plant are adapted to grow in different conditions, just like the Ebony which grow better in a low
salinity condition in the middle of the forest.
Thus, the islet has immense value as an area to protect a unique blend of species. It has no other
value other than conservation.
