MEPS prepress abstract  -  doi: 10.3354/meps07412

ABSTRACT: 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 days to 15 years, and using the tracks of followed groups over scales of 1–48 hr. The females/immatures made frequent movements of less than 2,000 km, and occasional movements of about 4,000 km. There were no recorded movements of greater than 5,000 km, for instance between the eastern and western Pacific. On average, females/immatures displaced about 4 km in 1 hr, 50 km in 1 day, 200 km in 3 days, and 1,000 km over periods of a year or more. Members of the two 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 hr, with one clan displacing about 50% more than the other. Displacements were greater than predicted by the correlated random walk over scales of 12–48 hr 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 to home ranges. The adaptive movement of sperm whales over large spatial and temporal scales likely contributes towards 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.