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Risso's dolphin

risso's dolphin

Scientific Name: Grampus griseus
Other Names: White-head Grampus, Grampus, Grey Dolphin
Length: 8.5-12.5 ft. (1.3-3.7 m.)
Weight: 660-1,100 lbs. (300-680 kg.)
Teeth: 4-14

This species has achieved modest fame through the exploits of 'Pelorus Jack', a Risso's dolphin that used to escort ships crossing Cook Strait between the two main islands of New Zealand between 1888 and 1912. He/she would meet nearly every ship between the two islands and escort them for several miles, riding the bow waves and/or cavorting along side. In recognition of this, the New Zealand legislature granted Pelorus Jack full governmental protection.
Most adult risso's dolphins are badly marked with scars, apparently caused by the teeth of other risso's dolphins.

This species was first named in 1812. The body has a dark grey back shading gradually to a pale grey or white belly. The greypales with age. The fin, flukes and flippers are black. The body is deep and massive in the anterior two thirds, but tapers markedly in the posterior third. There's a square-ended appearance to the head when viewed in profile, as a result of a large and bulging forehead. The fin is tall, narrow, pointed and slopes slightly backwards. It is situated just posterior to the halfway point along the body. The flippers are broad based and long.

There are no teeth in the upper jaw and no more than 12 in the lower jaw. The first 6 cervical vertebrae are fused.
Risso's dolphins may be found in all temperate to tropical waters, and have been stranded quite frequently off the coasts of the British Isles and America. They are fairly rapid swimmers and will jump out of the water. They usually stay under the water for only a few minutes but this can be extended up to half an hour. They tend to live in small groups of about 10 individuals but larger herds of up to 100 have been observed. They migrate towards the pole in summer, returning closer to the equator in winter. gramper

Little is known of their reproductive behavior but they are thought to give birth to calves in early spring in both northern and southern hemispheres.  They have been successfully kept and bred in captivity and have been trained to perform
tricks for public display. These dolphins have been known to make regular trips with boats.