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Site description (2004 baseline)
North Sentinel is a 4,700 ha, island that lies west of the Wandoor National Park (Mahatma Gandhi Marine National Park), while South Sentinel is only 161 ha, located further south. The hostile, indigenous Negrito tribe, the Sentinelese, inhabit North Sentinel, which is completely isolated from the rest of the world. They are the sole inhabitants of the island and successfully retain and defend their traditional lifestyle and pristine territory. They vigorously repel any attempt made by government teams or others to communicate with them, by aggressively attacking intruders in their territory (Gandhi 2000). South Sentinel Islands has been visited by many people but there is no permanent habitation, save the light house, as there is no source of fresh water on this small island. It was declared as a Sanctuary in 1997, primarily to protect the Giant Robber Crab Birgus latrao for which South Sentinel is the last stronghold in the Andamans. Every year, during March, thousands of Pied Imperial-Pigeon Ducula aenea come from the South and Little Andaman Islands to nest in South Sentinel. This IBA is also very important as a nesting habitat of the Green Turtle Chelonia mydas. It is surrounded by spectacular inter-tidal coral reefs, reef slopes and shelves, all of which are extensive and need to be assessed, according to Bhaskar (1993), Andrews (1997) (quoted in Andrews and Sankaran 2002). The forest is more or less intact in North Sentinel as man has not yet reached there, with his chainsaws and concept of “sustainable harvest”. As the Sentinelese have successfully deterred outsiders, the biodiversity of this island has not been studied or recorded. The island appears to be covered by dense tropical rain forests. It is evident that the forest and surrounding coast, which the tribals have protected for centuries, provide all their living requirements. South Sentinel Island is a small flat, coral island, where lagoons mark about half the length of the shore, the rest being rocky or sandy. The whole island, with the exception of a 36 ha swamp, is covered with dense Andaman Tropical Evergreen forest, which extends about 75 ha, consisting mainly of Sea Mohwa Manilkara littoralis, with an undergrowth of various smaller trees and shrubs. There is a well-defined sea fence, consisting of screw pine (Pandanus) and Hibiscus (Littoral Forest 50 ha) along the shore (Osmaston 1908, Seksharia 2000).

Key biodiversity

AVIFAUNA: Not much is known about the bird life of North Sentinel Island as the tribals resist the entry of outsiders, but South Sentinel has been visited by many naturalists and bird watchers. Osmaston (1908) visited it in 1907 to study the Pied Imperial Pigeon and Nicobar Pigeon Caloenas nicobarica. The former still nests in huge numbers all over the island, and the latter in small numbers. It is estimated that South Sentinel has at least ten Restricted Range species, of which one, the Andaman Crake Rallina canningi is globally Threatened. The endemic Andaman Teal Anas gibberifrons could be present (Ravi Sankaran pers. comm. 2002). In South Sentinel, one pair of White-tailed Eagle Haliaeetus albicilla, a Near Threatened species, has become an almost permanent feature.

OTHER KEY FAUNA: As mentioned earlier, North Sentinel has not been explored and we do not have any information on its fauna, but it is supposed to be largely intact, as the tribals sustainably harvest their needs. On South Sentinel, one of the flagship invertebrate species of the Andaman and Nicobar Islands, the Giant Robber Crab, is found in large numbers. It is nocturnal and spends the day time in large hollows of old Sea Mohwa trees, which are the dominant trees of the island.

Green Sea Turtle Chelonia mydas breeds on the long sea beach of South Sentinel (Seksharia 2000). Earlier, they used to “swarm round the island, coming on shore in the evening to lay their eggs” but now the population is not so large, at least around South Sentinel, due to extensive poaching by fishing trawlers. The Leatherback Turtle Dermochelys coriacea also occurs, but in smaller numbers. Saltwater Crocodile Crocodylus porosus and Andaman Water Monitor Varanus salvator andamanensis, are supposed to be common on both islands. The Andaman Emerald Gecko Phelsuma andamanense, also called Andaman Day Gecko, is active during the day, unlike most other geckos which are nocturnal. It has a peculiar distribution, being found not in mainland Asia but in the oceanic islands of Mauritius, Seychelles, Reunion and Madagascar (Daniel 2002). There is no indigenous terrestrial mammal, except the endemic Andaman Horseshoe Bat Rhinolophus cognatus.

Acknowledgements
Key contributors: Ravi Sankaran and Tara Gandhi.

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Recommended citation
BirdLife International (2024) Important Bird Area factsheet: North and South Sentinel (India). Downloaded from https://datazone.birdlife.org/site/factsheet/north-and-south-sentinel-iba-india on 22/12/2024.