Risso's Dolphin

 

Animal Unique | Risso's Dolphin | Risso's dolphins, also known as Grampus, is one of the larger members of the dolphin family. They are usually an offshore dolphin whose inshore appearance is unusual. They occur worldwide in temperate and tropical waters, mostly in the deep waters rather than close to land. Besides the tropical parts of the Indian, Pacific and Atlantic Oceans, Risso's dolphins are also found in the Persian Gulf, Mediterranean Sea and Red Sea, but not the Black Sea. They range as far north as the Gulf of Alaska and southern Greenland and as far south as Tierra del Fuego. Their preferred environment is just beyond the continental shelf on steep banks.

Scientific classification
Kingdom:     Animalia
Phylum:     Chordata
Class:     Mammalia
Order:     Cetacea
Family:     Delphinidae
Genus:     Grampus
Species:     G. griseus

Risso's dolphins have a relatively large front body and the dorsal fin, while the rear tapers to a relatively narrow tail. The bulbous head has a vertical crease in front. nfants its dorsal and ventral Igray cream to brown with a white anchor-shaped area between the pectoral fins and around the mouth. In older calves, the non-white areas darken to almost black, and then illuminate (except for the always dark dorsal fin.) Linear scars mostly on social interaction eventually most of the body cover. Older people seem mostly white. Most people have 2-7 pairs of teeth, all in the lower jaw.Like most dolphins, males are usually slightly larger than females.

Risso's dolphins are found in groups of 5-50 animals, but groups usually average between 10 to 30 animals. They have been reported as solitary individuals, pairs, or in loose aggregations in the hundreds and thousands. Occasionally this type associated with other dolphins and whales. They have been reported with other species such as Bottlenose dolphins, Gray whales, rRght whale dolphins Northern, and Pacific white sided dolphins. Due to the offshore distribution of this species, primary prey appears to be squid, although they are also known to feed on a variety of fish species. While the size of their prey is unknown squid, octopi have beaks of species that grow to 12 meters long was found in the stomachs of stranded  Risso's dolphins. They use the 2-7 pairs of peg-like teeth in their lower jaws to capture prey.

By catching in fishing gear is the main threat to  Risso's dolphins. Various types of gear, including gillnets, longlines and trawls, are documented to occasionally "take" the species. Historically, large numbers of Risso's dolphins slain associated with tuna purse seine fishing in the eastern tropical Pacific. This species is directly hunted for their meat and oil in Indonesia, Japan (fishery drive), the Caribbean (Lesser Antilles), and the Solomon Islands. The population in some of these areas where fishing and hunting interactions themselves may have declined in local abundance.

Risso's dolphins are generally not approaching boats, but occasionally bow wave surfing. A notable exception was a person named Pelorus Jack, who guided boats in Admiralty Bay, Marlborough Sounds in New Zealand for over 20 years. Hunting of this species has never been particularly widespread, and the species is recognized as an abundant and safe. Risso's have been successfully taken into exile in the United States, Japan and Italy, although not with the regularity of the bottlenose dolphins and orcas. Hybrid Risso's-rockers have been bred in captivity.

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