Besides what is known about common dolphins in general, little is yet known about the specific behaviour of the long-beaked dolphin (2). Common dolphins are amongst the most gregarious mammals and are sometimes seen in groups of more than 1,000 individuals (4) (6). These large schools may comprise smaller social units of 10 to 30 closely related dolphins (5). At the surface, common dolphins are extremely energetic, moving in and out of the water in a series of high speed jumps, known as porpoising, or leaping vertically to create a dramatic splash on landing (5) (6). Speeds in excess of 40 kilometres per hour can be reached and these dolphins will often ride the bow waves of ships (4) (5). Common dolphins typically dive for two to three minutes in the pursuit of food and can reach depths of up to 280 metres (4). A large geographic range accounts for a diverse mix of prey, that includes various species of small schooling fish and squid (4) (5) (6). Breeding usually takes place between spring and summer, with a sexually mature female giving birth every two or three years. The calf is born following a gestation period of nine to eleven months and is weaned after around six months. The age at which sexual maturity is reached appears to vary with region such that males may take two to seven years and females may take between three and twelve years. The maximum life expectancy is estimated to be around 22 years (4) (5).