Behaviour
A sperm whale Physeter macrocephalus feeding. © EOL
Sperm whale social units tend to comprise up to 15 mature females and their offspring, but larger aggregations of up to 30 may occur, possibly to enhance foraging opportunities (Best, 2007; Rice, 1989).
When threatened or attacked, sperm whales may gather into a circle with their heads pointing inwards and with calves protected in the middle (Jefferson et al, 2008).
Juvenile males separate from these mixed units around puberty, grouping together in so-called batchelor schools of up to 50 animals. As the males mature and grow larger, they detach from these batchelor groups and either become solitary or form much smaller groups of around 6 animals (Best, 1979).
Feeding
The major prey of sperm whales is cephalopods (octopuses, squid), though other invertebrates and fish have been found in stomach contents. Primary prey species include squids of the genera Architeuthis (giant squid), Moroteuthis, Gonatopsis, Histioteuthis and Galiteuthis (Jefferson et al, 2008).
Sperm whales are exceptionally deep and long divers. Dives of over 2000 metres lasting more than one hour have been recorded, though stomach contents recovered from one individual taken at 3193 metres contained the remains of a bottom-dwelling shark, suggesting deeper dives may be possible (Watkins et al, 1993).