This sanctuary declared a RAMSAR site in July 2010, is a 4,800 hectare wetland made up of four sections; the Puliyantivu Island, Tiruketiswaram, Pallimunai, Vankalai and the area on either side of the causeway that connects the island of Mannar to the mainland. A portion of this sanctuary is considered as an archaeological site dating back to the 6th century BC.
Its rich bio-diversity and arid-zone environment comprises thorny scrubland, sand dunes, tanks, waterholes, mangroves, marshes, lagoons and maritime grasslands. It is home and feeding ground to many species of water birds that include uncommon migrants such as the Gadwall, Spot-billed Duck and the Comb Duck, Long-toed Stint, Peregrine Falcon, Waterfowl and the Common-ringed Plover.
Other species found here would be the Oystercatcher, Great Knot, Avocet, Northern Shoveler, White-Winged Black Tern, Common Coot, Red Knot, Great Black-Headed Gull, Heuglin’s Gull, Pallid Harrier, Golden-Backed Woodpecker, Caspian Tern and many others.
Vankalai is also a haven to some threatened species of Marine turtles, Saltwater Crocodiles and rare Dugongs as well as over 60 species of fish are found in the rich ecosystems here at Vankalai, providing essential feeding and spawning grounds to them.