Lloyd F. Lowry

Seal eating by walruses in the Bering and Chukchi Seas

SummaryWalruses (Odobenus rosmarus) feed primarily on benthic invertebrates, but they are known to eat seals (Phocidae) occasionally, ostensibly when the benthic foods are unavailable. We investigated reports of a marked increase in occurrence of seal-eating walruses in the Bering Strait region in the late 1970s by examining stomach contents of animals taken in the spring harvests by Eskimos. We also obtained relevant information during visual surveys of marine mammals in the region. Our findings from the stomachs indicated that seal eating was 10 to 100 times more common during the 1970s and early 1980s (0.6–3.0%, N=645) than it had been in the previous three decades (0.07–0.20%, N=4015). In addition, we observed walruses in possession of seal remains in 1978 and 1979, where we had not seen such a phenomenon before in the previous 25 years. We attribute the increased predatory interaction between seals and walruses partly to a larger walrus population and, especially in 1979, to unusually restrictive spring ice conditions, which tended to cause greater than usual overlap of their distributions. Stomach contents of walruses taken in the Chukchi Sea in summer, where the ranges of walruses and seals overlap broadly in all years, have indicated a similarly high rate of occurrence of seal eaters (8.6% in the 1960s, N=35; 11.4% in 1983, N=44). As a whole, our findings indicate that most of the seal eating is predation, rather than scavenging of carrion. They also indicate that it is not rare or aberrant but common behavior, and that it could exert a significant impact on seal populations in some areas.

Movements and Behavior of Satellite- tagged Spotted Seals (Phoca largha) in the Bering and Chukchi Seas

Abstract Satellite-linked tags were attached to 12 spotted seals (Phoca largha) captured at a coastal lagoon in the eastern Chukchi Sea during August 1991–1993. Movements of seals were tracked for 32–298 days using the Argos system. Of 9,651 total location records obtained, 7,268 were usable. Individual seals were located on 41–96% of the days that tags were operational. During August–November, tagged seals alternated haul-outs at coastal sites lasting 1–304 h with trips to sea of 14–901u2009h. Coastal haul-outs occurred at 14 sites in western Alaska and eastern Russia. On several trips to sea, seals covered distances of more than 1,000u2009km. Movement southward from the Chukchi Sea generally began in October, with most of the seals passing through the Bering Strait during November. Seals first hauled out on sea ice in October (Chukchi Sea) or November (Bering Sea), and generally moved southward during October–December as sea-ice coverage increased. Seven seals, whose transmitters were still operating, spent December to June in the Bering Sea region between Kuskokwim Bay and Anadyr Gulf, which corresponded to the location of the ice front. The seals made active east-west movements within the ice front. Spotted seals are unlike other ice-breeding seals in that they regularly use coastal haul-outs during summer and autumn. Compared to the closely related Pacific harbor seal (Phoca vitulina richardsi), spotted seals make much longer trips to sea and spend longer continuous periods at their haul-outs during summer and autumn.

Notes on winter feeding of crabeater and leopard seals near the Antarctic peninsula

SummaryStomach contents of crabeater (Lobodon carcinophagus) and leopard (Hydrurga leptonyx) seals collected in the pack ice west of the antarctic Peninsula in August–September 1985 were analyzed. Food remains were found in 7 of 56 crabeater seals and 5 of 29 leopard seals. The primary foods were krill (Euphausia superba) which occurred in all 12 stomachs, and fish (Pleuragramma antarcticum) which occurred in 3. Eleven of the seals with food in their stomachs were collected in the southern portion of Bismark Strait. The incidence of feeding seemed highest in pregnant females. These results, and comparisons with previous collections, suggest that krill were not abundant or widely distributed in the area at the time the seals were collected. The sizes of krill eaten by crabeater and leopard seals were very similar, and were significantly larger than krill found in 2 samples taken by midwater trawls in nearby open water.