Risso's dolphins are widely distrubuted around the globe, but tend to be found offshore, towards deeper waters. They seem to stay near the edge of the continental shelf, and may be found close to shorelines of islands where the shelf is narrow. Their coloration varies from a very dark, almost black color, to a more common grey, with older animals appearing as a very pale grey, almost white. As a Risso's dolphin ages, it becomes covered with more and more scars on its body, probably caused by disputes with other members of the same species, though some might be the result of confrontations with squid, a primary staple of the dolphin's diet.
Risso's dolphin's do not have a prominant beak, or rostrum, as most dolphins do. Instead, their melon drops straight downwards to their mouth, giving their head a blunt appearance. The mouth line slopes upward towards their eyes at a steep angle, and there may be anywhere from four to fourteen teeth at the tip of their lower jaw. Their pectoral fins are long and slim, with pointed tips. From a distance, their tall dorsal fin may be confused with a female or juvenile orca, though up close, they are unmistakable.
Younger animals of this species are quite a bit more active than older individuals, and often breach quite a ways out of the water. Older Risso's dolphins have a tendency to not come quite so far out of the water, usually just slapping their heads against the surface. They're not active bow-riders, though they may swim alongside boats or in the wake of a passing vessel. One might also see these dolphins spyhopping, lobtailing, or porpoising as they swim. The average size of a group of Risso's dolphins is anywhere from 3-50 individuals, though several hundred may gather together for a short while.
last updated 7/15/00
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