of Bengal to the east, the Palk Straight to the south and swampy backwaters and salt pans to the west and north. Coordinates are between 10.276 and 10.826 N and 79.399 to 79.884 E. Low sand dunes are located along the coast and along the western periphery with coastal plains, tidal mud-flats and shallow seasonal ponds in between. Sand dunes in the east are mostly now stabilised by Prosopis and the higher dunes in the west are stabilised by dense Tropical dry evergreen forests. The tallest dune in the sanctuary and the highest point of land in Nagapattinam District is . at the northwest corner of the sanctuary at Ramar Padam. PCWBS forms the easternmost and most biologically diverse part of Ramsar Site no. 1210 which, on 19 August 2002, was declared a place of international importance for the conservation of waterbirds and their wetlands habitats. This site comprises PCWBS, Panchanadikulam Wetland, Unsurveyed Salt swamp, Thalainayar Reserved Forest and Muthupet Mangroves. It is all part of the Great Vedaranyam Swamp, except the reserved forest. Fauna This sanctuary is an area of high biodiversity, with many unique species of animals and birds. See photos Land animals PCWBS is inhabited by fourteen mammal species, eighteen reptile species and nine amphibian species. The flagship species of the sanctuary is the near threatened blackbuck antelope, one of the four antelope species in India (Chinkara, Chausingha and Nilgai being the other three) and the most numerous large animal in the sanctuary. The population estimate of the blackbuck at Point Calimere more than doubled in thirty years, from 750–800 in 1967 to 1,908 in 1998/99. This isolated population of blackbuck probably survived unmolested throughout the centuries due to the locals' now declining belief that eating its meat causes leprosy. The predators of the blackbuck at Point Calimere are jackals, and sometimes village dogs. Competition for food is from domestic and feral cattle. Other notable animals include: spotted deer, jackal, bonnet monkey, wild boar, monitor lizard, short-nosed fruit bat, small Indian civet, star tortoise, Indian grey mongoose, black-naped hare, jungle cat and feral pony. Marine animals Bottlenose dolphin is frequently seen along the shore of the sanctuary in morning and evening hours during the winter. The shoreline beaches of the sanctuary are a regular nesting site of the endangered olive ridley turtle. In 2002 a pair of Bryde's whale were found washed ashore near the sanctuary. One