Migration to breeding areas by male sperm whales Physeter macrocephalus from the Northeast Atlantic Arctic.

Mature male sperm whales (Physeter macrocephalus) primarily inhabit high latitude regions, travelling to tropical/temperate waters for breeding, where females and juveniles reside in cohesive social groups. Though mating is known to occur at low latitudes, the timing, duration, and routes of adult male migrations between feeding and breeding areas are poorly known. To study movement patterns of adult male sperm whales, 29 individuals were equipped with satellite transmitters in the Northeast Atlantic Arctic (69-79°N). Twelve of these animals undertook southward migrations. Departures from northern latitudes occurred asynchronously from January to October, indicating that sperm whales do not have a well-defined breeding season. Migrating males travelled 40 (± 11) d to reach the breeding areas at latitudes below 45°N. They travelled distances of 3,993-7,951 km. They spent 76 (± 22) d in the south, roaming across an enormous region (˃10 million km2). Dives deeper than 1,000 m occurred both during migration and at the breeding grounds. Two whales were tracked back to Arctic waters. Their trips took 175 and 180 d, with cumulative distances travelled being 16,332 km and 17,669 km, respectively. This study fills important knowledge gaps in the annual cycle of these cosmopolitan giants.