email a friend
printable version
Location Mauritius, Outer Islets
Central coordinates 57o 48.00' East  19o 49.00' South
IBA criteria A4i, A4iii
Area 31 ha
Altitude 0 - 162m
Year of IBA assessment 2001

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.

Key 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.

Populations of IBA trigger species

Species Season Period Population estimate Quality of estimate IBA Criteria IUCN Category
Sooty Tern Onychoprion fuscatus breeding  250,000-500,000 breeding pairs  A4i  Least Concern 
Brown Noddy Anous stolidus breeding  10,000-100,000 breeding pairs  A4i  Least Concern 
Lesser Noddy Anous tenuirostris breeding  10,000-100,000 breeding pairs  A4i  Least Concern 
A4iii Species group - seabirds breeding  1,000,000-2,499,999 individuals  unknown  A4iii   

Protected areas

Protected area Designation Area (ha) Relationship with IBA Overlap with IBA (ha)  
Ile aux Serpents Nature Reserve 31 is identical to site 31  

Land use

Land-use Extent (% of site)
nature conservation and research -

References Bell et al. (1994), Lloyd (1846), Newton (1960), Safford (1993b), Vinson (1950, 1953).

Contribute  Please click here to help BirdLife conserve the world's birds - your data for this IBA and others are vital for helping protect the environment.

Recommended citation  BirdLife International (2016) Important Bird and Biodiversity Area factsheet: Serpent Island. Downloaded from on 22/10/2016

To provide new information to update this factsheet or to correct any errors, please email BirdLife