THE DOLPHIN SWIM 17–20 MARCH 2025
THE
IRRAWADDY
DOLPHIN
Distribution
Irrawaddy dolphins inhabit sheltered coastal waters throughout Southeast Asia, including estuaries, mangroves, and deltas. In addition to their coastal presence, they have five distinct freshwater populations in Myanmar, Borneo, the Mekong River in Laos and Cambodia, India, and Thailand. Although not classified as true river dolphins, these populations exist hundreds of miles inland, far from coastal waters.
Behaviour & Ecology
Irrawaddy dolphins are typically seen in small groups of two to three, though larger groups of up to 15 individuals can occasionally be spotted. Their diet includes fish, shrimp, and cephalopods, which they hunt in shallow waters. While social, they are not very active at the surface but may occasionally perform low breaches. A unique behaviour involves spitting water, possibly to confuse schools of fish. In Myanmar, these dolphins engage in cooperative fishing with local fishermen, herding fish toward boats and picking off weaker individuals caught around the nets before they are retrieved.
Fun Facts
The Irrawaddy dolphin is named after the Ayeyarwady River in Myanmar, which was formerly known as the Irrawaddy River when Myanmar was called Burma.
In the Sundarbans, one of the world’s largest mangrove forests, Irrawaddy dolphins occupy the same habitat as Ganges River dolphins.
Coastal Cambodian populations occupy the same habitat as Indo-Pacific humpback dolphins and Indo-Pacific finless porpoises.
Laotian and Cambodian folklore suggest that Irrawaddy dolphins are reincarnations of their ancestors.
West Kalimantan people share stories of Irrawaddy dolphins being naughty children that stole rice from the shaman. When they burned their mouths and jumped into the river to cool down, they eventually turned into Irrawaddy dolphins.
Main Threats
Irrawaddy dolphins face multiple threats across the world primarily associated with habitat loss and human activities. Infrastructure development has isolated freshwater populations, confining them to smaller areas and reducing hunting opportunities, leaving them with only 40% of their original range. Coastal populations are similarly affected, as reduced water flow impacts estuaries and mangroves. Bycatch in gillnets is arguably the greatest threat, causing premature deaths. Pollution further endangers them, with industrial and domestic waste contaminating both freshwater and coastal habitats, leading to skin abnormalities in six populations.
The Irrawaddy River Population
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Prefer deeper areas of lakes and large rivers
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Less than 100 adult individuals left
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The population and range of the dolphins has declined greatly in the last 39 years
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Habitat monitored by WWF-Cambodia’s River Guard Programme
IUCN STATUS:
The Irrawaddy Marine Population
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Marine dolphin populations inhabit coastal areas, particularly muddy and brackish waters,
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Unknown population size (ongoing research by Khmer Ocean Life)
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Population threatened by human activities like bycatch
IUCN STATUS:
The Irrawaddy Dolphin in Cambodia