Risso's Dolphins were discovered in 1812. A man named Mr. Risso described this species to Culvier in 1812, thus giving this dolphin its name. The Risso's Dolphin is also known as the Grampus. This particular dolphin is found worldwide in warm-temperate and tropical waters. Commonly this dolphin is spotted in deep waters and rarely close to shore lines. You'll find the Risso's Dolphins in the Atlantic, Pacific and Indian Oceans, along with the Mediterranean, Red and Black Seas.
The Risso's Dolphin is a large full bodied mammal with a large head somewhat rounded head. This dolphin has a distinctive crease that runs from the melon on its head, to their mouths. The bodies of these dolphins is very similar to the Pilot Whales. An adult Risso's Dolphin has a typical length of 10 feet, but have been recorded at 12.5 feet. The average weight is 650lbs., but have been recorded to weigh as much as 1100lbs. It appears that the male Risso's Dolphin is the larger between the themselves and the females.
When Risso's Dolphins reach a length of 8.5-9.2ft in length, sexual maturity appears to be reached as well. It is also assumed that they are less than 13yrs. of age when this length is reached. Evidence through studies done in the North Atlantic Ocean shows calves are born in the summer months after a gestation period of 13-14 months. Calves are born 4-5ft. long. Calves are light grey when born, darkening to a brownish-grey as they mature, eventually becoming fully dark grey with a white anchor shaped patch running from their throats to their stomachs when their adults.
Pods are typically groups of 3-30 dolphins but larger pods of 3000 dolphins have been spotted. The Russo's Dolphins primarily feed on squid but are known to also known to feed on numerous fish specied available to them accordingly with where they are located, as well.
The Risso's Dolphins have been captured and sustained in captivity in both the United States and Japan. Both the Risso's and Bottlenose Dolphins have been bred within captivity to create a hybrid species named, Risso's-Bottlenose Dolphins.
The Risso's Dolphins are killed for human consumption in some areas of the world, most noteably, Taiwan. Their population numbers don't appear to be threatned due to a study conducted in the waters around Central and Northern California. Here the population numbers appeared to be between 13,000-30,000 dolphins. More research is needed to better understand this dolphin species.