Risso's dolphin

Grampus griseus

Risso's dolphin Risso's dolphin
One of the larger members of the Delphinidae family, the Risso's dolphin can be easily identified because of the numerous white scars throughout its body, which can make some old individuals look almost completely white.
The scars are actually teeth markings caused by other individuals and, to a lesser extent, the result of fighting with squids (the Risso's dolphin's favourite food).
Other characteristic features of this species are:
  1. Rounded head, with bulging forehead and no beak
  2. Very tall, falcate dorsal fin, located half-way between head and tail
  3. Long, sickle-shaped flippers (pectoral fins)
  4. Large, relatively robust body, which becomes more slender behind the dorsal fin
  5. Vertical crease, running from the blowhole down to the top of the mouth
Risso's dolphins can sometimes be confused from distance with Orcas, Pseudorcas and even Bottlenose dolphins, primarily because of the shape of their dorsal fin.
At close range, though, the differences among the above mentioned species become more evident and confusion should not arise.
Not very acrobatic, young individuals are seen breaching far more often than fully grown adults. Also, the Risso's dolphin very seldom bow-rides, and strongly prefers to surf in wakes and waves.
Lobtailing and flipper slapping are not uncommon.
This widely distributed dolphin prefers waters with temperatures above 10°C (50F), along areas where the continental slope is steeper.
In the Azores it can often be seen very close to shore.
The diet is primarily based on squid, but it is also known to eat small fish.
Interestingly, Risso dolphins often swim side by side and spread out forming a long line when hunting.