Large-scale sexual segregation of bowhead whales

Abstract

Skin biopsy samples from 806 bowhead whales Balaena mysticetus collected between 1995 and 2010 at 4 locations in Nunavut, Canada, and at 1 locality in West Greenland were used for determination of sex and sexual segregation of bowhead whales in the Baffin Bay stock. There was a significant dominance of females in the Disko Bay samples (78%), whereas the sex ratio in aggrega- tions in Nunavut was not significantly different from 50:50. Data on the body length of whales sug- gest that primarily large mature whales without calves occupy Disko Bay, whereas primarily mother- calf pairs are found in Foxe Basin. On a broader scale, Baffin Bay is more widely used by adult males and resting or pregnant females from Disko Bay, while Prince Regent, Gulf of Boothia, Foxe Basin, and northwestern Hudson Bay are also used by nursing females, calves, and sub-adults. The most parsimonious explanation for the large-scale spatial segregation of sexes in bowhead whales is that mature females without calves utilize Disko Bay as a foraging ground during certain parts of their reproductive cycle. Acoustic recordings of singing males indicate that Disko Bay may also be a mat- ing ground, where some males may be following estrous females into the bay.