Risso's dolphins belong to the Mammalian Order Cetacea, in the
suborder Odontoceti. All toothed whales belong to the suborder
Odontoceti, which is Latin for "toothed whales". This dolphin
belongs to the oceanic dolphin family, Delphinidae. Other members
of this family include the killer whale, long-beaked common dolphin,
and pilot whale. Risso's dolphin's scientific name is Grampus
griseus. The generic name, Grampus, is probably derived
from the Spanish grand pez, meaning "great fish". The
specific name, griseus, is derived from the Latin gris,
meaning "gray". This refers to the gray coloration of the animal.
This animal is named for Antoine Risso (1777-1845), a French
Risso's dolphins reach 9-12ft in length and 900-1000lbs in weight.
Adults are grayish in color, with darker dorsal and pectoral fins.
The underside and melon are lighter. Large white streaks mark the
dolphin's entire body. These are healed scars from aggressive
engagements with other Risso's dolphins. Risso's dolphin has a
bulbous head with no prominent beak.
Native to all temperate and tropical ocean waters, Risso's dolphin
prefers the deep, open ocean. Their diet consists primarily of
squid and fish.
of 12 or fewer Risso's dolphins are commonly observed. Migration to
cooler waters may occur during the summer months. Calving appears
to take place during the warmer months. Newborn calves are 4-5ft in
length and are solid gray in color. Calves are solid gray because
they have not been subjected to the same scarring as adults.
Risso's dolphin is
thought to be quite numerous worldwide, with the exception of a few
regions. Although not directly hunted by American fisherman,
Risso's dolphin is commercially exploited by Japanese and Filipino
fisheries. Gillnets are a common threat to Risso's dolphin
throughout Southeast Asia.