Ecology of the Weddell Seal in McMurdo Sound, Antarctica

• Published in: Ecology
• Main Author: Stirling, Ian
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1969
• Subjects: Antarctic; Arctic; McMurdo Sound; The Antarctic; Weddell; Antarc*; Antarctica; Leptonychotes weddelli; Phoca hispida; ringed seal; Sea ice; Weddell Seal; Weddell Seals
• Online Access: http://dx.doi.org/10.2307/1936247; http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.2307%2F1936247; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.2307%2F1936247; https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.2307/1936247

The object of this paper is to discuss the relationship of the Weddell seal (Leptonychotes weddelli) to its habitat, the fast ice of Antarctica. Movements and distribution of Weddell seals during summer are governed by presence of fast ice and availability of breathing and exit holes. It is suggested that this applies during winter also. Local populations are relatively discrete and there is limited emigration and immigration. This is supported by demonstration of significant genetic differences in blood serum transferrins from seals at McMurdo, Mawson, and Wilkes. My data support the hypothesis that the Weddell seal is not migratory but moves as the distribution of breathing holes during winter dictates. Subadults were shown to be distributed further out on the fast ice than adults. Inaccessibility and potential danger involved in reaching this area have resulted in a paucity of sightings of subadults and given rise to the theory that they migrated to the pack ice. The location of pupping colonies is determined by physical factors, mainly glacial movement and tidal action, independent of biological considerations such as exposure or accumulation of drift snow. Adult females show a high degree of fidelity to particular colonies for pupping in successive years. During the pupping season, seals are spaced in the pupping colonies and nonbreeding seals and subadults are excluded from these areas. After weaning of pups, and probably mating of adult females, the mean distance between seals on the sea ice is reduced and subadults are tolerated in these areas by adults. Even so, there is a higher proportion of adults than subadults at new cracks which continually form south of the pupping colonies through the summer. This is probably due to competition for a new food source. The behavior and movements of the Weddell seal in the fast ice of the Antarctic are almost identical to those of its ecological counterpart, the ringed seal (Phoca hispida) in the Arctic and are interesting examples of parallel evolution.