The Irrawaddy dolphin is a euryhaline species of oceanic dolphin found in discontinuous subpopulations near sea coasts and in estuaries and rivers in parts of the Bay of Bengal and Southeast Asia.
The Irrawaddy dolphin is similar to the beluga in appearance, though most closely related to the killer whale. It has a large melon and a blunt, rounded head, and the beak is indistinct. The dorsal fin, located about two-thirds posterior along the back, is short, blunt, and triangular. The flippers are long and broad. It is lightly coloured all over, but slightly more white on the underside than the back. Unlike any other dolphin, the Irrawaddy's u-shaped blowhole is placed on the left of the midline and opens towards the front of the dolphin. Their short beaks appear very different than those of other dolphins, and their mouths are known for having 12-19 peg-like teeth on each sides of their jaws.
Their short beaks appear very different than those of other dolphins, and their mouths are known for having 12-19 peg-like teeth on each sides of their jaws. Irrawaddys can range from 90 kg (200 lb) to 200 kg (440 lb) and length is 2.3 m (7.5 ft) at full maturity. Maximum recorded length is 2.75 m (9.0 ft) of a male from Thailand.
There are plenty of food items that this dolphin feeds upon. They include fish, crustaceans, and cephalopods. They do this sometimes while spyhopping and during feeding, apparently to expel water ingested during fish capture or possibly to herd fish.
These dolphins are thought to reach sexual maturity at seven to nine years. In the Northern Hemisphere, mating is reported from December to June. Its gestation period is 14 months; cows give birth to a single calf every two to three years. Length is about 1 m (3.3 ft) at birth. Birth weight is about 10 kg (22 lb). Weaning is after two years. Lifespan is about 30 years.
Irrawaddy dolphins are shy of boats, not known to bow-ride, and generally dive when alarmed. They are relatively slow moving but can sometimes be seen spyhopping and rolling to one side while waving a flipper, and occasionally breaching. They are generally found in group of 2-3 animals, though sometimes as many as 25 individuals have been known to congregate in deep pools. Groups of fewer than six individuals are most common, but sometimes up to 15 dolphins are seen together.