The movements of female and immature sperm whales Physeter macrocephalus in the tropical Pacific Ocean and adjacent waters are described using photoidentifications over time scales of 3 d to 15 yr and the tracks of followed groups over scales of 1 to 48 h. The female/immature whales frequently made movements of less than 2000 km and occasionally made movements of about 4000 km. There were no recorded movements of greater than 5000 km (for instance, between the eastern and western Pacific). On average, displacements for female/immature whales were about 4 km after 1 h of movement, 50 km after 1 d, 200 km after 3 d, and 1000 km after periods of 1 yr or more. Members of the 2 principal cultural clans of female and immature sperm whales that use waters near the Galápagos had distinctive movement patterns over all time scales greater than 3 h, with 1 clan's displacements about 50% greater than the displacements of the other. Displacements were greater than predicted by the correlated random walk over scales of 12 to 48 h because of autocorrelation in displacement, approximately as predicted by the correlated random walk over periods of days to weeks, but less than predicted by the correlated random walk over scales of years because of boundaries of home ranges. The adaptive movement of sperm whales over large spatial and temporal scales likely contributes to their substantial trophic impact, and reduces geographic population structure. These movements, together with cultural heterogeneity, complicate the management of the species, including the designation of management stocks.KEY WORDS: Sperm whale · Movement · Culture · Density-dependent habitat selection · Population structure Resale or republication not permitted without written consent of the publisher

We studied the social structure and mating system of sperm whales (Physeter macrocephalus L., 1758) off northern Chile over 10 months in 2000, photographically identifying 898 individuals. The mean size of encountered groups of females with immatures was about 23 animals, while the estimated mean size of units (sets of females and immatures with permanent relationships) was 11 animals. About 4% of the population consisted of large mature males, although this varied seasonally. Groups of females and immatures, as well as large males, spent only a matter of days within the study area at a time. There was no evidence for preferred ranges for the males, for males consistently accompanying particular groups, or for males forming coalitions. Males roved between the groups of females and immatures. Both mature males and females or immatures appeared to take the initiative in maintaining or breaking close associations. These results are similar to those from studies off the Galápagos Islands, even though the habitat, nonsocial behaviour, and relative abundance of mature males were quite different in the two areas.

Sperm whale movements, residency, population structure, and behavior were investigated in the Gulf of California in 1998 and 1999. Variations in sperm whale movement patterns and behavior were related to changes in prey abundance (jumbo squid, Dosidicus gigas) determined by fishery statistics. Photo-identification data revealed that seven female sperm whales moved into the Gulf of California from the Galipagos Islands, traveling up to 3,803 km. These are among the longest documented movements for female sperm whales. There were significant differences in speed and distance traveled during a dive cycle between 1998 and 1999 (low and high squid abundance). In 1999 there were also significant differences in small-scale movements and behavior between the northern and the southern part of the study area (high and low prey abundance). These results suggest that when food resources are low, sperm whales travel in straighter lines, dive for longer periods, travel larger distances during dive cycles, and at higher speed. In 1999 there were significant differences in time spent socializing in areas of high prey abundance versus areas of low abundance. All of these changes in behavior were consistent with increased foraging effort when squid abundance was low. A high proportion of mature males and first-year calves were observed in the Gulf of California, suggesting that it is an important sperm whale breeding ground.Analysis of variation in behavior and movement patterns in relation to changes in food supplies is critical to our understanding of a species' ecology. The 545

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