The Irrawaddy Dolphin (Orcaella brevirostris), commonly thought to belong to the river, is in fact a euryhaline species of oceanic dolphin. Nevertheless, it has grown to symbolize the magnificence of the Mekong River and its continued high biodiversity.
Irrawaddy dolphins in appearance similar to the Beluga, So they are more closely related to the Orca. This is a particularly distinctive dolphin; it has a large lovely rounded head with no beak and a flexible neck with visible creases behind the head. The dorsal fin, located about two-thirds posterior along the back, is short, blunt and triangular. The flippers are long and broad. A mature dolphin can grow to about 275cm and weighs about 200kg.
Irrawaddy Dolphin Population
The latest population survey showed that only 80 Irrawaddy Dolphins inhabit the Mekong River, but even this low number would make the Mekong sub population the largest of only five remaining critically endangered freshwater populations of this species in the world. They have chosen the rivers in the province of Kratie and parts of Stung Treng to be their home and it is here in Kratie, that tourists flock to observe these beautiful rare dolphins.
Irrawaddy Dolphin Behavior
These dolphins are less active than many other dolphin species and are believed to be reincarnated humans by some people in Asia. With only the uppermost dorsal surface of the animal becoming visible on slow rolling dives, they make only occasional low leaps and never bow-rides like other species often do. These dolphins can dive for up to 12 minutes at a stretch.
Mostly feeding always done in groups of usually less than six and they feed mostly on bony fish, crustaceans, cephalopods and fish eggs. They are intelligent beings; the Irrawaddy dolphins that known to spit water to herd fish, and have even been reported to stun large fish with blows from their lower jaws, only to play with them before casting them aside, sometimes without eating them.
Although in some areas of Asia, fishermen consider the Irrawaddy dolphin to be a competitor for fish, in other areas, traditional fishermen attract them to their boats and encourage them to drive fish into their nets in response to acoustic signals from them. In return, the Dolphins which rewarded by preying on fish confused by the nets and those that are momentarily trapped around the edges. This mutual relationship in co-operative fishing is dying out as the number of these wonderful creatures dwindles in the wild.
Little is known about the reproductive biology of the Irrawaddy dolphin, but they are thought to reach sexual maturity at 7 to 9 yrs old. They breed between December and June and gestation is estimated at 14 months. At birth, a young dolphin weighs about 12.3kg and is about 96cm in size.
The Irrawaddy dolphins are indeed lovely creatures whether or not they are reincarnated human. In Cambodia, these charming and intelligent creatures swim free in the rivers of Kratie and Stung Treng as they are very well protected by law.
Tour boats ferry visitors to where the dolphins roam and guests are
often rewarded the bonus of a beautiful Kratie sunset.