Serpent Island (6659)
Mauritius, Africa

Site overview

KBA status: confirmed

Global KBA criteria: B1, D1a

Year of last assessment: 2001

National site name: Serpent Island

Central coordinates: Latitude: -19.8167, Longitude: 57.8000

System: marine, terrestrial

Elevation (m): 0 to 162

Area of KBA (km²): 0.28433

KBA classification: Global

Legacy site: Yes

Site details

Site description: Serpent Island is the most remote and inaccessible of the five northern islets of Mauritius (area given as 19 ha in some publications). The islet is in the shape of a dome (162 m high) with a circular base and extremely steep slopes. The lower slopes are marked by hollows, overhangs and ledges, with low cliffs around the shore, whereas the upper slopes are relatively smooth. Vegetation is almost absent; the three plant species recorded are all rare, although common elsewhere. A thin coating of guano covers the rock surface. Landing is extremely difficult. As on Round Island, exotic rodents have never become established. However, a vast colony of surface-nesting seabirds covers the whole islet and this, combined with the near-absence of vegetation, gives Serpent Island a totally different character. It has an ecosystem of vertebrates and invertebrates, many perhaps endemic to the islet, most living independently of any vegetation.

Rationale for qualifying as KBA: This site qualifies as a Key Biodiversity Area of international significance that meets the thresholds for at least one criterion described in the Global Standard for the Identification of KBAs.

Additional biodiversity: See box for key species. The seabird colony consists mainly of terns (Sterninae). Populations are very large (estimated totals up to 850,000 pairs), but have never been reliably censused. Around 50 pairs of Sula dactylatra (of the scarce Indian Ocean race melanops) are also present. Unusually for the region, Anous tenuirostris nests on the ground. Pterodroma arminjoniana visits from nearby Round Island, but has not been proven to breed. Phaethon rubricauda formerly bred and may still do so occasionally. The island has no potential for landbirds. Non-bird biodiversity: Reptiles: Nactus serpensinsula (VU) (islet-endemic subspecies; species otherwise occurs only on Round Island), Gongylomorphus bojerii (possibly islet-endemic subspecies). Arachnids: undescribed lizard-eating tarantula Pterinochilus sp. (Theraphosidae). Other islet-endemic invertebrates likely to be found.

Delineation rationale: Type 1 marine IBA: suitable for the seaward extension approach.

Habitats

Land use: nature conservation and research

Threats

Summary of threats to biodiversity at KBA: The islet is a Nature Reserve and access is strictly forbidden to all but authorized researchers. The difficulty of landing on the island has proved its best form of protection (though landing is prohibited anyway). No rehabilitation is needed, as the island is in a close-to-pristine state, and landbird introductions are not possible. The seabirds are affected by poaching from time to time, although this appears spasmodic. Establishment of rats (if this is possible at such a site) could endanger many species on the island.

Additional information