The dusky dolphin is a highly social species, sometimes found in herds of over 1,000 individuals, although groups of 20 to 500 are more common (3). Large groups often come together to cooperatively hunt prey, which is quite varied and includes anchovy, squid and shrimp. The species may also feed at night. The dusky dolphin frequently associates with other cetaceans (2) (3) (6), and is said to be one of the most acrobatic of all dolphins, readily approaching boats to bow-ride, and often leaping high out of the water and tumbling in the air (3). Mating is believed to occur in spring, with a single calf born after a gestation period of 11 months (6) and measuring around 55 to 70 centimetres at birth (3) (6). Births usually peak in summer (November to February) around New Zealand and Argentina, and in winter (August to October) around Peru (2). Calves are weaned at around 18 months (6).