RISSO'S DOLPHIN
(Grampus griseus)Identification
Size
- to a maximum of 4 m
Colour
- mostly grey, with white on the belly
- dorsal and pectoral fins are dark grey
- body is usually covered with many scars and scratches; older animals may appear completely white
Dorsal fin
- large, dark grey dorsal fin, resembling that of a female killer whale
Blow
- small and bushy
Surface behaviour
- may porpoise, spyhop or breach
- Unlike other dolphins, they rarely bow ride
Group size / social behaviour
- social, usually in groups of 10 – 50 animals. Most sightings of Risso’s dolphins in BC are of groups with less than 25 animals.
Other characteristics
- very robust head with a prominent “melon”, contrasting with a thin tail stock
Can be confused with
- killer whales or pilot whales (but color is very light grey; killer whales and pilot whales do not typically have a multitude of scars and scratches)
Natural History
The Risso’s dolphin feeds almost entirely on squid. They have been found to depredate fish from long lines. They can be found in mixed groups with Pacific white-sided dolphins and Northern right whale dolphins.
The life history of this species has been little studied, but sexual maturity is thought to be attained at 8-10 years for females and 10-12 years for males. Intervals between calves average 2.4 years, and gestation is approximately 13 months. Lifespan is 35+ years.
Status in Canada
COSEWIC: Not at Risk
BC Provincial Red List: Yellow (Apparently secure and not at risk of exteinction)
