Intersexual differences in the postbreeding foraging behaviour of the Northwest Atlantic hooded seal

Abstract

Sexual dimorphism and different reproductive strategies lead males and females to forage differently among a wide range of species. We used dive and location data collected from 23 hooded seals Cystophora cristata captured in the Gulf of St Lawrence (Canada) during the period from March to June, 1992 to 2005, as proxies for foraging behaviour. Females spent 12 d longer than males in the Gulf before undertaking their migration to Greenland. Females and males greatly overlapped on a horizontal scale but were segregated on a vertical scale, females diving on average 70 m shallower than males during the few weeks preceding the migration and 40 m deeper than males following the migration. Both sexes spent similar amounts of time diving and showed significant diel variation in dive depth but remained at significant depths at night (>200 m), suggesting that both sexes foraged mostly on benthopelagic prey. The relatively minor differences in foraging behaviour observed between sexes may be explained by similar mass loss during the reproduction and the constraints related to the extensive annual migration.