Spinner dolphins move about the oceans in schools; groups that vary in size from just a few dolphins to over a thousand. They commonly school with other species such as pantropical spotted dolphins, or small toothed whales (5). In such schools, spinner dolphins are known to undertake migrations, following prey or warm water currents (8). In Hawaii, spinner dolphins usually spend their days resting in shallow bays near deep water, and then move offshore at dusk and feed as they move substantial distances along the shore (8). Pelagic spinner dolphins feed primarily on small mesopelagic fish, squids and shrimps, and dive down to depths of 300 meters to catch their prey (8). The dwarf spinner dolphin feeds on reef fishes and other benthic organisms (7)
Mating in spinner dolphins appears to be promiscuous, and like many small dolphins, true courtship behaviour can be observed, such as mutual caressing between the male and female (9). The breeding system may vary geographically, with some populations showing a greater degree of polygyny than others (10). Calves are born every three years, after a gestation period of about ten months (2). The mother nurses the calf for up to two years (2), and they form a bond that lasts a lifetime (8). Females reach sexual maturity between four and seven years, whereas males do not reach maturity until between seven and ten years (2).
The purpose of the energetic spinning behaviour of the spinner dolphin is not known. It has been suggested that the large cloud of bubbles created by the powerful spin and splash landing may act as an echolocation target, to allow a widely dispersed school of dolphins to communicate (5). Another theory is that the spinning may dislodge hitch-hiking remoras, or the spinning may, at times, simply be play (5).