Dynamics of an isolated population of Weddell seals (Leptonychotes weddellii) at White Island, Antarctica

A small population of Weddell seals (Leptonychotes weddellii) was studied at White Island, Antarctica, where it is apparently isolated from other populations of Weddell seals by 18 km of floating glacier ice. The seals at White Island have increased from only nine in 1968-1969 to 26 seals older than pups in 1993-1994, with a concurrent decline in body condition. No evidence of immigration or emigration was found. Higher survival of adult seals, lower fecundity, and higher mortality of pups occurred at White Island relative to seals in an open population only 30 km away in Erebus Bay. High neonatal and preparturient mortality at White Island, including pups with congenital deformities, suggest that genetic viability of this population is questionable. If it remains isolated, the population of Weddell seals at White Island is a model for small populations of endangered seals and possibly for conditions leading to speciation in polar phocids.