Status of pinnipeds on mid-Atlantic ridge islands, South Atlantic Ocean

Abstract

The status of pinnipeds on mid-Atlantic ridge islands is reviewed to detect trends that may relate to climate change. Small numbers of southern elephant seals Mirounga leonina breed on Gough Island (40°S, 10°W) and at Bouvetoya (54°24′S, 03°21′E) where numbers remained small over ~ 68 years. Vagrant southern elephant seals wandered farther north to tropical Saint Helena Island (15°57′S, 5°41′W) in historical times but have not been recorded there more recently. This suggests a contraction of their distributional range, as manifested in the decline in numbers to imminent extinction at Gough Island. At Gough Island and at Tristan da Cunha (37°05′S, 12°17′W), leopard seals Hydrurga leptonyx and Antarctic fur seals Arctocephalus gazella are occasional seasonal transients from Antarctic and sub-Antarctic islands and the circumpolar sea ice farther to the south. Large populations of Antarctic fur seals A. gazella and sub-Antarctic fur seals A. tropicalis breed at Bouvetoya and Gough Island, respectively. The current state of both populations is uncertain as other populations of conspecifics in the South Atlantic and South Indian oceans are in decline ostensibly contingent upon reduced food availability, likely precipitated by climate change.