Overview
Risso’s Dolphin (Grampus griseus) is an extraordinary, heavily scarred oceanic cetacean renowned for its unique, blunt-headed silhouette and striking ghostly white appearance. Navigating deep submarine canyons and continental drop-offs worldwide, this cephalopod-hunting specialist lives a rough-and-tumble life, accumulating hundreds of crisscrossing white scars from social sparring and deep-sea squid tentacles until elderly adults appear almost completely snowy white.
Biology and Physical Characteristics
Grampus griseus is easily identified by its bulbous, squared-off melon bisected by a unique vertical crease down the forehead, completely lacking a beak. It features a tall, falcate dorsal fin resembling that of a female orca. Calves are born sleek and dark slate-grey, but as they mature, social interactions with herd-mates’ teeth and the suckers of giant squids carve white, non-pigmented scar tissue across their body, whitening them with age.
Behavior and Ecology
A dedicated nocturnal deep-diver, Risso’s Dolphin spends daytime hours resting and socializing in pods of 10 to 30 individuals along steep underwater drop-offs. At night, when bioluminescent squids migrate toward the surface, the pod embarks on deep foraging dives to 600 meters, using powerful biosonar clicks to track and suction-feed on slippery squids with only two to seven pairs of peg-like teeth located exclusively in the lower jaw.
Conservation and Human Impact
Classified as Least Concern by the IUCN, Risso’s Dolphin benefits from an extensive pelagic range far from coastal human activity. However, it is vulnerable to oceanic driftnet bycatch, military naval sonar disturbances, and significant bioaccumulation of heavy metals from its long-lived squid prey.
Interesting Factoid
Elderly Risso’s Dolphins look like ghostly white sea phantoms; they accumulate so many white battle scars from squid tentacles and teeth that older individuals appear completely pure white from head to tail.