Freshwater rivers, such as the Irrawaddy and Mekong in Southeast Asia, and the shallow tropical zones of the Indian and Pacific oceans, constitute the habitat of the Irrawaddy dolphin (Orcaella brevirostris). In the Mekong they now inhabit just a 190km stretch in the north of Cambodia, and can be spotted most easily at Kampie and north of Stung Treng near the Laos border, with occasional sightings elsewhere. In 2001, a pair were found just a few kilometres north of Phnom Penh.
Irrawaddy dolphins look more like porpoises than marine dolphins, with rounded heads and foreheads that protrude slightly over a straight mouth; noticeably, unlike their seagoing cousins, they have no beak. They’re also more languid than their marine cousins, rarely leaping out of the water, chasing after boats or displaying any of the other skittish personality traits commonly identified with their species.
Irrawaddy dolphins reach maturity around the age of 5 years, when they can measure up to 2.75m in length and weigh up to 200kg. Family groups, or pods, usually consist of around six individuals, but larger groups are not unknown. In spite of good breeding rates, there is a high rate of calf mortality, which remains unexplained.