The offshore islets off the mainland of Mauritius are today the only places where the original native flora and fauna subsist. As it is, the biodiversity of Mauritius evolved over millions of years giving rise to its specific endemism and diversity. Yet, since humans settled on the island 400 years ago, most of the endemic plants and animals have gradually disappeared, including the Dodo bird. What few native animal and plant species remain today are located on the offshore islets thus resulting in many of them currently declared as national parks and nature reserves. In line with this, currently, 8 offshore islets are proclaimed as National Parks and 7 as Nature Reserves.
Before Mauritius was inhabited, the mainland and the surrounding islets were vibrant with life. As people began to develop the land for agriculture and settlement, forest land was cleared for such activities. Invariably, this led to the loss of many plant and animal species especially the small reptiles. Yet, the most damaging impacts came from introduced animals including deer, pigs, hare and rabbits. They destroyed the understory forests, preyed on animals’ eggs and young ones and damaged their habitats. Also, amongst these animals, the black rats (Rattus rattus) are believed to have caused the most ecological damage on the islets.
Moreover, many of the offshore islets were used in the past for human purposes such as quarantine grounds or enemy watch-out points. In this way, the fragile biodiversity of the islets was heavily impacted as settlements and infrastructure were built. Likewise, movement from island to island resulted in the introduction of pests and weeds. As the foreign species proliferated, they competed with the local ones for food, space and even preyed on them. As a consequence, several plants and animals disappeared such as the Burrowing Boa on Flat Island.
Nevertheless, compared to the mainland where less than 2% of the native forest remains, some of the native jungle still exists on many islets that were not exploited by humans. In fact, each one of the several islets around Mauritius has its own unique characteristics and is home to different species. For instance, the Telfair’s Skink is restricted to Round Island only today when in the past it was distributed over several other islets. As it currently stands, many of these islets are the last places of Mauritius where the coastal palm forest and several reptiles species remain.
In terms of conservation strategy, the offshore islets of Mauritius with the highest ecological values are basically categorized into national parks and nature reserves. A national park is a geographical area protected by the state for the long term preservation of its natural resources. A nature reserve is a protected zone either by the state or privately for its flora, fauna and natural resources.
In Mauritius, the offshore islet national parks and their average sizes are Ile d’Ambre (128 ha), Ilot Fouquets (2.49 ha), Ilot Vacoas (1.36 ha), Ilot Flamants (0.8 ha), Ile aux Oiseaux (0.7 ha), Ilot Fous (0.3 ha), Pigeon Rock (0.63 ha) and Rocher aux Oiseaux (0.1 ha).
Furthermore, the offshore nature reserves including their average sizes are Flat Island (253.26 ha), Round Island (168.84 ha), Gunners Quoin (76 ha), Gabriel Island (42.21 ha), Serpent Island (31.66 ha), Ile aux Aigrettes (26 ha) and Ilot Mariannes (4.05 ha).
Ile d’Ambre offshore islet National Park is situated on the north-east of Mauritius and is easily accessible from the mainland. It is home to a rich forest of mangroves and is also a well-known eco-tourism site where residents and tourists enjoy kayaking through the mangrove trees. Though the islet has been heavily degraded in the past, today some endemic Latanier Bleu (Latania loddigesi) trees still remain.
Located in the Mahebourg bay on the south-east coast, Ilot Fouquets is a small offshore islet with historical importance. Given its strategic position in the bay, it played an important role in spotting enemies during the naval battle at Grand Port back then. The islet has a distinct inclined topography and the high grounds are separated from the low grounds by a sandy channel. A lighthouse is found on the elevated land and native vegetation grows on the lower side. In addition to this, Ilot Fouquets is an important site for nesting birds.
Also found in the Mahebourg bay, Ilot Vacoas too played an important role in the historical naval battles. It has a small beach accessible to visitors and is an important site for nesting shearwaters. Some native plants still grow on the islet and a few reptiles like the Bojer’s skink, Bouton’s skink and the Nactus gecko also subsist there.
The small Ilot Flamants is basically a sandbank found off the south-eastern coast. Formed by coral pieces and sand, virtually no plants and animals inhabit the islet as it is subject to frequent overtopping of waves and tides. Nevertheless, in the past, there has been a lot of sand mining there. Thus, the protective status of the islet inhibits all sorts of illegal activities with a long term vision of a growth in size.
The small Ilot Oiseaux is a sandbank within a semi-enclosed coral reef located in the Mahebourg bay as well. The lagoon between it and Ilot Flamants is considered valuable for conservation.
This tiny islet in the Mahebourg bay is unhospitable and can only be accessed at low tide and during calm weather conditions. As it is, Ilot Mariannes, Ilot Fous and Rocher des Oiseaux were once a single island which eventually got submerged due to sea-level rise. In general, Lesser Noddys roost on Ilot Fous and the shoreline purslane (Sesuvium ayresii) is the only plant species that grow on it.
As the name suggests, Pigeon Rock is simply a huge rock that immerses out of the sea. This interesting feature is actually a volcanic plug which occurs when magma solidifies inside a vent of an active volcano. Pigeon Rock is an important refuge for seabirds such as the Wedge-tailed shearwater, red-tailed tropicbird and the white-tailed tropicbird.
Rocher aux Oiseaux is also a massive rock that juts out of the sea. It is very dangerous to land on the islet because of its particular pitted limestone nature. Moreover, violent waves constantly break on the pitted rocks making ventures on the grounds quite dangerous.
As the largest of the northern islets, Flat Island has unique conservation importance and is also a common destination for catamaran cruises. Additionally, the surrounding sea is quite rich making snorkelling an unforgettable experience. In the main, the island is a common breeding site for many seabirds, has some of the original coastal forests and is inhabited by native reptile species like the Ornate day gecko and the Bojer’s Skink.
Quite contrary to its name, Round Island is not round but rather an offshore islet that is ecologically very rich. Basically, this small islet off the north coast of Mauritius stayed free from rodents resulting in little impact on its ecosystem. Still though, in the past goats and rabbits were introduced on the islet and they damaged some of the native biodiversity. But the eradication of these mammals and stringent conservation measures has resulted in the restoration of the coastal palm-rich forest and the preservation of important animal species.
To date, at least 10 threatened native plant species are found on Round Island including the Vacoas (Pandanus vandemeerschii) and the Palmiste bouteille (Hyophorbe lagenicaulis). Also, two species of skinks, two species of geckos and two boa snakes inhabit the islet. It is also the only known location in the Indian Ocean where the Round Island Petrel breeds.
Located in the north of Mauritius, Gunners Quoin is a small islet that has an interesting whale shape. Many native plant species grow there such as the Mazambron marron (Lomatophyllum tomentorii) and the Acacia indigene (Gagnebina pterocarpa). Some small palm savannah pockets also exist. It is also a common breeding site for the white-tailed tropicbird, the red-tailed tropicbird and wedge-tailed shearwaters. Moreover, the lesser night gecko (Nactus coindemirensis) also lives on Gunners Quoin.
Gabriel Island is a small islet in the north of Mauritius and is a common cruise destination for its beautiful marine life and calm beaches. It is mostly covered by coastal dune vegetation and is the only place where the Baume de l’ile Plate (Psiadia argute) grows. Gabriel Island has the highest percentage of native plant species compared to the other northern islets and quite a good population of white-tailed tropicbirds. In addition to these, native reptiles like the Bojer’s Skink, the Snake-eyed skink and the ornate day gecko inhabit the island.
Though it bears the name of Serpent Island, no serpent actually lives on this small islet off the north coast of Mauritius. Basically, this rocky islet has almost no vegetation and is mostly home to seabirds including the brown noddy (Anous stolidus), the sooty terns (Sterna fuscata) and the lesser noddy (Anous tenuirostris). Serpent Island is also home to the Nactus gecko and a tarantula species that has not yet been identified.
Ile aux Aigrettes is one of the most famous island reserves in the Mascarenes. Situated on the south-east, this small islet still has some of the original native forests with rare trees like the Bois d’Ebene (Diospyros egrettarum), Bois Chandelle (Dracaena concinna) and the Bois de Boeuf (Gastonia mauritiana). Managed by the Mauritian Wildlife Foundation (MWF), restoration works have been undertaken to remove weeds and eradicate rats. Ile aux Aigrettes serves as educational and ecotourism site attracting school students and tourists alike. Amongst the animals, giant tortoises help in weed control and 20% of the native Pink Pigeon population inhabits the forest. Recently, a population of the critically endangered Mauritian Fody was released on the islet.
This small islet reserve is found on the south-east of Mauritius off the coast of Mahebourg. Together with Ilot Fous and Ilot Oiseaux, Ilot Mariannes is referred to as the Ile Mariannes System. Though the ecosystem is not unique, the biodiversity is particular to this specific coralline islet environment. Shearwaters nest on the islet and several seabirds also visit it though there are no permanent bird residents. The native green-backed Heron and the Whimbrel also frequently fly around the islet. Also, 29 vascular plant species have been identified on Ilot Mariannes including the Veloutier blanc (Argusia argentea), a dwarfed Veloutier vert (Scaevola taccada) and the Bois matelot.