Home › Sea Wildlife › Marine Species › Mammals › Irrawaddy River Dolphin
[Phylum: Chordata] [Class: Mammalia] [Order: Artiodactyla] [Family: Delphinidae (snubfin dolphins)]
One of the rarest and most charismatic ocean mammals found in South and Southeast Asia is the Irrawaddy river dolphin.
It's not a "true" river dolphin (such as those in the Amazon), but it is a coastal and estuarine species named after the Irrawaddy River in Myanmar, where these osmoregulators were first discovered.
The Irrawaddy dolphin is one of only five species of river dolphins still in existence today.
Besides the Ayeyarwady (aka Irrawaddy) River in Myanmar, Orcaella brevirostris are also found in:
This euryhaline species of oceanic dolphin actually prefer slow-moving, shallow water systems where there's an abundance of fish.
According to the WWF, there are less than three hundred (300) Irrawaddy river dolphins still remaining outside of captivity.
They are types of marine mammals that inhabit some of the coastal areas, estuaries, and freshwater river bodies in the Bay of Bengal and parts of Southeast Asia.
Irrawaddy dolphins can be identified by the grey body colouring (slate blue top and pale underneath), a rounded forehead, and a blunt snout.
Here's the thing:
They lack the long beak which is typical in most species of dolphins (cetaceans). But it's the short, blunt nose and gentle smile that give them the friendly appearance.
The small dorsal fin, positioned towards the back of the body, can make them difficult to spot in turbid and murky waters.
Adults grow to a total body length between two (2) and three (3) metres (up to 9 feet long) and typically weigh between 90 and 200 kilograms (up to 440 pounds).
Irrawaddy dolphins generally live in small pods of two to six individuals. They are intelligent and extremely social with humans.
In fact, fishermen and river dolphins have developed some notable partnerships in Myanmar and Thailand. When the dolphins herd fish toward nets, they get to eat any of the catch that escapes.
Despite the occasional bottom-feeding traits, the generalist diet of Irrawaddy dolphins is one that consists mostly of bony fish (especially catfish), crustaceans, and cephalopods (squids, octopus).
Populations of the Irrawaddy river dolphin have severely declined in recent years. Some of the contributing factors include:
In actuality, only a few dozen individuals remain in some river systems. However, the conservation efforts that are underway are focusing on community-led fishing practices, animal awareness programs, and habitat protection.
The IUCN Red List of Threatened Species last assessed the Irrawaddy dolphin (Orcaella brevirostris) in 2017. They classified them as "Endangered" with a "Decreasing" population trend.
But wait - there's more:
One of their closest relatives, the Australian snubfin dolphin (Orcaella heinsohni) was also assessed by the IUCN in 2017. They list them as "Vulnerable" with the number of mature individuals estimated to be less than 10,000.
Many dolphin species hold cultural significance for local communities. They are essential indicators of healthy river ecosystems.
Their presence reflects the balance that exists between nature and harmful human activities. Hence, the protection and conservation of Irrawaddy dolphins is not only a matter of species survival, but also one of cultural heritage as well as ecological integrity.
Mekong Irrawaddy dolphins represent a decreasing isolated population of the Irrawaddy River Dolphin. It inhabits a stretch of the Mekong River, mainly between Kratie and the Khone Falls region near the border separating Laos and Cambodia.
This population of endangered mammals is one of only a few verified groups of Irrawaddy dolphins that will spend their entire lives in freshwater.
They also have similar characteristics with other Irrawaddy dolphins. Their forehead is rounded, there is no beak, and a small, curved dorsal fin is set far back.
Fully grown adults can reach a length of 2.5 metres (8 feet) and weigh up to 130 kilograms (290 pounds). Their skin is gray and smooth, and it sometimes glistens when they break the surface of calm river waters.
Mekong Irrawaddy dolphins are social and slow-moving creatures. They are often seen in small pods of up to six (6) individuals.
Fun Fact: They feed mainly on fish and crustaceans found in the deep pools and they use clicks and whistles to communicate with each other.
The population of the Mekong Irrawaddy dolphin is critical and endangered. Recent estimates suggest fewer than one hundred (100) individuals remain.
Note: The short video [2:41 minutes] presented by "Deep Marine Scenes" contains even more Irrawaddy dolphin facts with footage of endangered aquatic mammals that enjoy helping fishermen.