Risso’s dolphins | ©Justin Hart (Azores - North Atlantic)
Grampus griseus (Delphinidae), the Risso’s dolphin, is one of the most enigmatic cetaceans, this little-known dolphin has an unusual appearance. Unlike many other dolphins, Risso’s dolphin lacks a beak, and the bulbous head rises almost vertically from the upper jaw and blunt snout . Along the body axis on the melon (the organ in the rounded head used to direct sonar clicks) there is a slight concave groove which is a unique characteristic of this species .
Risso’s dolphin may also be recognized from the extensive lines of white scar tissue that stretch down the sides of the body. These are thought to be caused by bites from other Risso’s dolphins during playing or fighting, although some of the scars may be the result of squid bites .
Grampus griseus has an extensive distribution. The species can be found in temperate, subtropical and tropical waters of oceans worldwide .