Sperm whales (Physeter macrocephalus) have one of the most extensive global distributions of any cetacean, but distribution and movement patterns vary significantly between sexes. Adult male sperm whales are predominantly solitary and have an expansive distribution, whereas females and their offspring typically form groups of both sexes, remaining in the tropics and sub-tropics throughout the year. Here we present observations and photographs from a rare winter sighting of a group of female and immature sperm whales near Koniuji Island, in the Central Aleutians, in the high-latitude waters of the Bering Sea. This sighting is consistent with historic whaling catches of sperm whales of both sexes, including pregnant females, above 50°N in the North Pacific, but no groups of females and immatures have been observed in ten years of summer sighting surveys in the Aleutian Islands and Bering Sea region, despite regular sightings of adult males. We discuss possible reasons for the absence of recent sightings of these mixed schools.
