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The Irrawaddy Dolphin

The Irrawaddy Dolphin (Orcaella brevirostris) population in several areas around the world is listed under the IUCN as being critically endangered. These incredibly shy creatures are more vulnerable as compared with other dolphin species due to their choice of habitat.

Sir Richard Owen first identified the Irrawaddy dolphin in 1866. Sightings were frequent in those days along the Irrawaddy River in Burma (Myanmar). The Irrawaddy dolphins are most likely to be found along coastal lands and rivers although they are oceanic and not true river dolphins. Living in these areas, they are more so threatened by human activities than other open seas roaming species ~ especially from being caught in fish gillnets; by explosives used for fishing; electric fishing using high voltage to kill anything in the waters; destruction of their habitat by creating dams upriver and also leaching of pollution from goldmines, untreated sewage etc; and removal of individuals for aquariums.

These dolphins are found in shrinking range of coastal areas in Burma, India and coastlines in a few South East Asian countries including Southern Thailand, Borneo ~ Sarawak, Borneo ~ Kalimantan at Mahakam River, to the Philippines and Northeastern Australia. Although the range is vast, the populations in these individual habitats are extremely small and steadily declining.

The Irrawaddy dolphin looks more like a beluga whale than the spinner or bottle nosed dolphins we normally see, accompanying boats on the open seas. Its scientific name, Orcaella (= little orca) describes it to be genetically linked to the Orca or Killer Whale and also describes its unique physical appearance unlike other dolphin species (brevirostris = short beaked).

These dolphins travel in groups of 2 to 6 individuals but in Sarawak, groups of about 10 individuals are often sighted around the Santubong and Buntal coastal areas. However, gatherings of as many as 30 individuals have been sighted before in the area due to congregation of different pods around the river estuary.

The Irrawaddy dolphins are slow moving, gentle creatures. The colour varies from light to dark grey and adults grow to 2.1 – 2.6m in length, weighing from 90kg to 150kgs. It’s not easy to spot the dolphins when the waves are choppy or when it’s raining as this causes too much surface disturbance. The dolphin generally does not breach (ie leaping out of the water) or spyhop (ie holding its head and upper body above water). When it surfaces for air, its movement is discreet. As it surfaces, it rolls over, showing only its rear half of the body, with its head still submerged. This causes a mere ripple on the surface..not a splash, and no performances. Once it emerges, it does 2 – 3 rolls and occasionally lifts its tail fluke above water in preparation of a deeper dive. The Irrawaddy dolphin can stay submerged for up to 12mins but typically dive some 30secs to 2mins each time.

Its diet consists of crustaceans, fish, cephalopods and fish eggs and in shallow waters, it forages on the sea bed for prawns and octopus.

Much is not known about the Irrawaddy dolphin like its reproductive habits or why is it that its stomach is compartmentalized and it also does not have a cardiac sphincter. They are thought to reach sexual maturity at 7 to 9 yrs. Its gestation period is 14months, giving birth to a single calf every 2 to 3 years. The lifespan of the dolphin is believed to be up to 30years.

Research is being conducted on the Irrawaddy dolphins in Burma (Myanmar) but little is known about the population in Sarawak. The dolphins on the Irrawaddy river have developed working relationships with the local fishermen in some areas to herd in fish. These methods of working together and recognizing signs has been passed down for generations from father to son and dolphin(female) to calf. The tapping on the side of the boat, the gurgling sounds and the smacking of the oars on the water surface by the fishermen and in reply the flicking of their fluked tails. This mutual understanding and respect between man and dolphin is a special bond and the local fishermen swears by it that they harvest more fish with the dolphins around than without them.

In Sarawak, the Irrawaddy dolphins and man have not developed such a relationship. Despite that, the dolphins are often seen tailing fishing boats for meals. These fishing boats normally separate their catch aboard and unwanted fish stock is thrown back into the sea, where the dolphins would be waiting to feast on these easy pickings.

Although the Irrawaddy dolphin is a Totally Protected Species, there are still perils in the water such as being caught in the trawlers’ netting. There is much scope for research to be done in river estuaries at Santubong, Semantan, Bako, Muara, Tebas, Kabong, Rajang and Igan and also upriver in Sadong, Bintulu, Miri and Limbang. The  population here can be sustained as there may be more scope for conservation work here.. with many more local people becoming aware of the dolphins existence in these waters - through the eco tours and kayaking trips available, the media and help of volunteers, maybe the Irrawaddy dolphins will be able to ride the waves of these tumultuous times and emerge one of few species to survive the current accelerated rate of species extinction.

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