Last Updated on 04/25/2024

The Irrawaddy dolphin is an oceanic dolphin species that predominantly inhabit brackish waters. This euryhaline dolphin can be found in rivers and estuaries in Southeast Asia and especially in the Bay of Bengal.

The Irrawaddy dolphin belongs to the Cetacea order and Delphinidae family. Alongside its cousin, the Australian snubfin dolphin, it belongs to the Orcaella genus. The scientific name of this dolphin is Orcaella brevirostris, which is Latin for short beak. The species was first described in 1866 by Sir Richard Owen, with the description being based on a specimen from 1852.

This dolphin closely resembles the beluga, but genetically, it is much closer to the killer whale. The dolphin has a large melon, a structure made of adipose tissue that is used for communication as well as echolocation. The head is round and the beak is short and barely distinguishable. It has a short, blunt triangular dorsal fin and long and broad flippers. The body colors are usually light shades of grey, with whiter areas on the underside.

This dolphin has a unique U-shaped blowhole which opens to the front of the dolphin rather than vertically, as is the case with most other species. The short beak has jaws with 12 to 19 teeth each. Adults can weigh from 90 to 200 kg and can reach lengths of over 2.3 meters.

Even though it is named after the Irrawaddy river in Myanmar, it is not a true river dolphin, but an oceanic dolphin. However, this species is euryhaline, meaning that is has evolved to be able to live in waters of various salinities, from brackish waters found in estuaries to marine waters. There are subpopulations living in the Bay of Bengal waters, from Bangladesh to India, Cambodia, Philippines, Indonesia, Thailand, and Myanmar.
Feeding

This species has a diverse diet, ranging from cephalopods to crustaceans and fish. The dolphin catches its prey by using echolocation, emitting sounds at a frequency of 60 kilohertz which bounce back and are picked up by the melon structure.

Individuals reach sexual maturity between seven and nine years of age. Females and males search for a mate for several minutes, copulate for 40 seconds after which they part ways. Cows have a gestational period of 14 months and they give birth to a calf which weighs 10 kg and is one meter long. Weaning occurs after about two years. Irrawaddy dolphin individuals can live for up to 30 years.

The Marvelous Irrawaddy Dolphin: A Comprehensive Overview

The Irrawaddy dolphin, renowned for its unique appearance and gentle nature, holds a special place in aquatic biodiversity. Known scientifically as Orcaella brevirostris, this dolphin species dwells in the freshwater rivers and coastal areas of Southeast Asia and South Asia. Its distinctive features and behavior make it a beloved creature in the regions where it resides.

1. Physical Characteristics

The Irrawaddy dolphin is characterized by its robust body, which is predominantly gray with a lighter underside. Unlike its oceanic relatives, this dolphin lacks a prominent beak and instead boasts a rounded forehead, giving it a melon-shaped head. Adult dolphins can grow up to 2.75 meters in length and weigh between 90 to 200 kilograms.

2. Habitat and Distribution

Preferably found in freshwater systems, Irrawaddy dolphins can be spotted in rivers, lakes, and coastal areas across Southeast and South Asia. Their range stretches from the Bay of Bengal to the northeastern coastline of Australia, encompassing major river systems like the Mekong, Ayeyarwady, and Mahakam.

3. Diet and Feeding Habits

Primarily piscivorous, the Irrawaddy dolphin’s diet consists of a wide array of fish, including catfish and carp. Additionally, they are known to consume crustaceans such as prawns. Their hunting technique involves herding fish using their flippers, ensuring a collective feeding experience.

4. Reproduction and Lifecycle

The mating season for Irrawaddy dolphins typically occurs during the cooler months. After a gestation period of about 14 months, females give birth to a single calf. Calves remain dependent on their mothers for milk and protection for an extended period, establishing a strong mother-calf bond.

5. Conservation Efforts

Despite their widespread distribution, the Irrawaddy dolphin faces significant threats, primarily from habitat loss, pollution, and unintentional catch in fishing gear. Various conservation initiatives aim to preserve their natural habitats and promote sustainable fishing methods to reduce the risk to these dolphins.

6. Cultural Significance

The Irrawaddy dolphin holds cultural and spiritual significance in several Southeast Asian communities. In Cambodia, they’re considered water spirits, and their sightings are deemed auspicious. Their gentle nature and playful antics also make them popular among tourists, boosting the local ecotourism industry.

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