Risso's Dolphin

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Risso's Dolphin
Conservation status
Data deficient (DD)
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Subclass: Eutheria Order: Cetacea Suborder: Odontoceti Genus: Grampus Species: G. griseus
Binomial name
Grampus griseus (G. Cuvier, 1812)
Risso's Dolphin range

The Risso's Dolphin (Grampus griseus) is the only species of dolphin in the genus Grampus.

[edit] Taxonomy

Risso's Dolphin was first described by Cuvier in 1812. The species' common name is for Mr. Risso who described a specimen to Cuvier on which Cuvier made his first description. Another common name for Risso's Dolphin is the Grampus (also the species genus) - although as a common name was historically used to describe the Orca. The etymology of the word grampus is unclear. It may be an aglomeration of the Latin grandis piscis or French grand poisson both meaning big fish. The specific name griseus refers to the mottled (almost scarred) grey colour of the dolphin's body.

[edit] Population and distribution

It is found worldwide in temperate and tropical waters, usually in deep waters rather than close to land. As well as the tropical parts of the Indian, Pacific and Atlantic Oceans, Risso's are also found in the Mediterranean and Red Seas, though are absent from the Black Sea. Their preferred environment is just off the continental shelf on steep banks (with water depths varying from 400-1000m) with water temperature at least 10° C and preferably in excess of 15° C.

The population around the continental shelf of the United States has been recorded to be in excess of 60,000. In the Pacific a census recorded 175,000 individuals in eastern tropical waters and 85,000 in the west. No global estimate of population exists.

[edit] Human interaction

Risso's Dolphins generally do not approach boats. A notable exception was an individual named Pelorus Jack who accompanied boats in Admiralty Bay in New Zealand's Marlborough Sounds for more than 20 years. Whaling of this species has never been particularly widespread though operations off Sri Lanka may be significantly damaging the local population. Globally the species is recognised as abundant and safe.

Risso's have been taken into capitivity successfully in the United States and Japan, though with nowhere near the regularity of Bottlenose Dolphins or Orca. Hybrid Risso's-Bottlenose Dolphins have been bred in captivity.

[edit] References

• Cetacean Specialist Group (1996). Grampus griseus. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 10 May 2006. Database entry includes justification for why this species is listed as data deficient
• National Audubon Society Guide to Marine Mammals of the World ISBN 0-375-41141-0
• Encyclopedia of Marine Mammals ISBN 0-12-551340-2
• Whales, Dolphins and Porpoises, Mark Carwardine, ISBN 0-7513-2781-6

• Risso's Dolphin Photograph, Jens Kuhfs Photography