PHYSIOLOGICAL-EFFECTS ON DIVE PATTERNS AND FORAGING STRATEGIES IN YEARLING WEDDELL SEALS (LEPTONYCHOTES WEDDELLII)

Fifteen yearling Weddell seals (Leptomychotes weddellii) were captured , measured, weighed, bled, equipped with time-depth recorders, and rel eased to determine if diving behavior was related to physical conditio n. Upon recovery of the time-depth recorders, dives were classified in to four types based on shape, using cluster analysis. Based on maximum depth, two groups were further subdivided, for a total of seven types . The mean and maximal dive depth, duration, and frequency were determ ined for each yearling for all dive types combined and for each type s eparately. Stepwise regression and ANOVA techniques were used to test the relationship between diving behavior and physiological and morphom etric measurements. In general, half of the variation in the pooled di ving behavior could be explained by body-size differences. Larger year lings made longer and shallower dives than smaller yearlings. Dive pat terns suggested that large yearlings foraged primarily on small shallo w-water prey items, while small yearlings concentrated on energy-dense deep-water prey. However, the interpretation of diving behavior, fora ging locations, and diet that resulted from separating individuals and dive types was very different from that based on average diving behav ior. This argues against ignoring variation among individuals and usin g only average diving behavior when describing marine mammal dive patt erns.