Sunday, August 7, 2011

Life of Pantropical Spotted Dolphin

Life of Sea | Pantropical Spotted Dolphin (Stenella attenuata) | Pantropical spotted dolphins spend the majority of their day in shallower water typically between 300 to 1,000 feet (90 to 300 m) deep. At night they dive into deeper waters to search for prey. They are distributed in tropical and warm-temperate waters around the world.  They live in north to Massachusetts, the islands of Cape Verde, the northern Red Sea, Persian Gulf, Arabian Sea, Bay of Bengal, South China Sea, East China Sea, Pacific coast of northern Honshu, the Hawaiian Islands, and Baja California Sur. Vagrant to Santa Cruz County in California, and Cold Bay on the Alaska Peninsula. They also range from south to Argentina, Cape Province in South Africa, Timor Sea, New South Wales, and about southern Peru. 

Pantropical spotted dolphin has three subspecies: E. Pacific offshore spotted dolphin, subsp A, Hawaiian spotted dolphin, subsp B, and the Eastern Pacific coastal spotted dolphin. There is also the Atlantic spotted dolphin. Both are named "spotted dolphins" due to the spotted patterns on their bodies that usually grow denser with age. They differ regionally by size and color, and tend to be more heavily spotted in the eastern Pacific than in the Hawaiian Islands where they have virtually no spots. The spotted dolphins of Japan and the eastern Indian ocean are moderately spotted. Spotted dolphins have a long slim beak with 35-48 small conical teeth in each side of the upper jaw and 34-47 small conical teeth in each side of the lower jaw. The spots begin to appear at the onset of weaning as dark blotches on the ventral surface. Closer to puberty, the spots increase in number and size and pale spots on the dorsal side begin to appear. Spotting varies among these species. Those with very dense light spots can appear white from a distance.

Pantropical spotted dolphins are hunted for food in Asia, Indonesia, the Phillippines, and parts of the Pacific. They often occur in groups of several hundred to one thousand animals. They are considered quite gregarious, often schooling with other dolphin species, such as spinner dolphins. Although specific migratory patterns haven't been clearly described, they seem to move inshore in the fall and winter months and offshore in the spring. They feed primarily on mesopelagic cephalopods and fishes. Pantropical spotted dolphins become prey for the Killer whale (Orcinus orca) and a number of shark.

Pantropical spotted dolphins are fast swimmer that often engages in a range of aerial acrobatics and will frequently ride the bow waves of boats, except for in tuna fishing grounds where it has learnt to avoid vessels. Juveniles in particular are known to make astoundingly high vertical leaps out of the water. While the breeding system of this species is not known, it is possible that it may be promiscuous, like that of the closely related Spinner dolphin . Every two to three years, mature female pantropical spinner dolphins give birth to a calf, after a gestation period of around 11 months. The calf is nursed for between one and two years. Females reach sexual maturity at 9 to 11 years, while males become sexually mature between the ages of 12 and 15 years.

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