 Adult males who are not breeding live solitary lives, whereas females and juvenile males live together in groups. The main driving force for the sexual segregation of adult sperm whales is scramble competition for mesopelagic squid. Females and their young remain in groups, while mature males leave their "natal unit" somewhere between 4 and 21 years of age. Mature males sometimes form loose bachelor groups with other males of similar age and size. As males grow older, they typically live solitary lives. Mature males have beached themselves together, suggesting a degree of cooperation which is not yet fully understood. The whales rarely, if ever, leave their group.
