dolphins whales community
IRRAWADDY DOLPHIN
Orcaella brevirostris
Classification:
The Irrawaddy dolphin is closely related to the Australian snubfin dolphin, and the two were only recently recognised as distinct species. As well as marine populations, there are five distinct freshwater populations of Irrawaddy dolphin; Mahakham, Ayeyarwady and Mekong Rivers, Songkhla Lake and Malampaya Sound. The relatively small size of the Irrawaddy dolphin, its mobile ‘expressive' head and its ability to spit water when instructed have unfortunately made this species popular in captivity in recent years.
Appearance:
The Irrawaddy dolphin is robust with a round melon, no beak, and a mouthline that angles up, giving it a smiling appearance.
It has a long flexible neck, allowing it to turn its head from side to side, a distinct neck crease, and a small triangular dorsal fin with a blunt tip. The flippers are large and spatulate, with curved leading edges and rounded tips.
The Irrawaddy dolphin has a uniform dark blue-grey to medium grey or pale blue colouration, with a paler underside.
Some individuals are lighter all over, giving them the appearance of a small beluga, only one with a dorsal fin.
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Behaviour:
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 have been seen spitting water from their mouths in the wild, and this behaviour is thought to help them hunt by confusing schools of fish.
They are generally found in groups of 2-3 animals, though sometimes as many as 25 individuals have been known to congregate in deep pools.
Other names:
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n/a
1.
Maximum length:
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Male: 2.75m
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Female: 2.3m
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Calf: 1m
2.
Maximum weight:
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Male: 130 kg's
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Female: Unknown
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Calf: 10 kg's
3.
Diet:
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Fish
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Cephalopods
4.
Estimated population:
Unknown
5.
Distribution map:
Distribution:
The Irrawaddy dolphin is distributed across the coastal Indian Ocean from India to Indonesia.
It prefers deep pools of large rivers, sheltered inshore marine waters with substantial freshwater inputs, like mangrove swamps and lagoons, and partially isolated brackish or freshwater bodies.
They are never found more than a few miles offshore and individuals have been found more than 1,300km upstream, with some spending their entire lives in fresh water.
Irrawaddy dolphins are principally threatened by incidental mortality in gillnets and other fisheries gear, although prey depletion, habitat alteration and pollution from agrochemicals are all believed to be taking a toll.