The adorable Risso’s Dolphin, Grampus griseus, ranks among the largest of all known species of dolphin. However, they have not been widely studied due to their preference for inhabiting deep ocean waters.
People once thought that the dolphin to be quite rare since they would hardly ever see it. Thankfully, evidence now indicates that they remain (surprisingly, given man’s hunting habits) present in great numbers, throughout many of the world’s oceans.
As many as 30,000 of the Grampus griseus perhaps inhabit the ocean waters adjacent to the coast of California, United States, alone.
Risso’s Dolphin Physical Characteristics
Sexual Dimorphism is present among the Risso’s Dolphin, but only to a small extent. The males are slightly greater, attaining a length of as much as 12.5 ft (3.8 m). They sometimes weigh as much as 1,100 lb (500 kg) but average only about 659 lb (300 kg). That is a big dolphin.
The flippers are comparatively long and slender in shape. The head is much more rounded than that of most dolphins, with a distinctive crease in the sonar-detecting organ known as the melon.
Their natural coloring is primarily a dark gray. However, adults often display extensive white patches, as a result of scarring from encounters with prey and potential predators.
Risso’s Dolphin Habitat and Ecology
The Grampus griseus primarily inhabits warm waters and appear to primarily inhabit regions near continental shelves.
The Risso’s Dolphin is a long-lived cetacean species with many individuals living as long as 40 years. A typical group (known as a pod) contains as many as 30 individuals. Yet, some super-pods could contain as many as 4,000. What a sight that would be.
They will feed on a variety of fish species, but their favorite prey is small species of squid.
Though information is scarce, the Risso’s Dolphin appears to have few natural predators itself.