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)

 

Notes

  • feed almost entirely on squid
  • have been found to depedate fish from long lines.
  • Can be found in mixed groups with Pacific white-sided dolphins and Northern right whale dolphins
  • 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.
  • Listed as Not at Risk in Canada by COSEWIC , BC Yellow list.