Spinner dolphin (Stenella longirostris), are small dolphins which belong to the family of Delphinidae. These species grow up to a size of 1.8 m in length and weigh up to 75 kilograms on average, whereas their maximum size can be up to 2.1 meter and weigh up to 95 kg. These species vary in their shape, size and color according to the geographical location. They have slender body with a long and thin beak, which is black on the upper part and white beneath. Their flippers are generally small and pointed at their tip. These dolphins are of light grey or dark grey with white belly.
Distribution and Habitat
These species occur in tropical and sub-tropical oceans. The largest populations of spinner dolphins are found between the Tropic of Capricorn and the Tropic of Cancer and mainly found in the waters of Hawaii. These creatures are found in the groups of hundreds and thousand in the eastern tropical Pacific Ocean. They live in the deep ocean where they track prey. These species rest in bays and other protected areas during the day time. At night they move in groups to feed on squids and fish.
These dolphins are carnivorous in nature and feed mainly on squids, shrimps and different mesopelagic fish. They dive up to a depth of around 300 meters to catch their prey. These creatures are also known to feed on reef fishes and other organisms. Their sharp and pointed teeth, which are about (45 to 65) in numbers, are present on each side of upper and lower jaws. They are known to feed mainly at night.
Breeding / Reproduction
The females of these species reach sexual maturity at the age of about (4 to 7) years, whereas the males reach sexual maturity at the age of about (7 to 10) years. The mating in these species takes all year round and the gestation period is about 12 months. One female may mate with the multiple males. They give birth to calves at the interval of (2 to 3) years. At the time of giving birth to the calves the female comes to the surface and as soon as the calf is born the mother takes it to the surface, so that it could take its first breath. The calf remains with its mother up to the age of about (3 to 8) years.
These spinner dolphins have suffered a huge population loss as they are entangled in the nets of tuna fishermen. The fishermen tried to catch these dolphins on a large basis due to which it decreased their number. In the eastern tropical Pacific region, the population of these species has decreased up to 80 %. The population of these species has come down from 2 million to 40,000. Now, these fishes are being conserved in captivity as well. These dolphins are displayed in Hong Kong, U.S., Philippines and Indonesia. All species of dolphin are protected under CITES (Convention on International Trade in Endangered Species).