The Irrawaddy dolphin (Orcaella brevirostris) is a unique marine mammal found in coastal areas, estuaries, and rivers across parts of the Bay of Bengal and Southeast Asia. These dolphins possess a distinctive appearance, characterized by a large, rounded head without a prominent beak and a short, triangular dorsal fin located further back on their body. Their coloration typically ranges from slate blue to slate gray, with a slightly lighter underside. Unlike many other dolphin species, their U-shaped blowhole is situated on the left of the midline and opens towards the front.
Global Population Estimates
The Irrawaddy dolphin is listed as “Endangered” on the IUCN Red List, with several of its freshwater subpopulations classified as “Critically Endangered.” Accurately counting these elusive animals presents a challenge due to their often fragmented habitats and shy nature. Recent estimates provide insight into their precarious numbers.
The largest known population resides in Bangladesh, with approximately 3,500 individuals in coastal waters of the Bay of Bengal and an additional 451 in the brackish Sundarbans mangrove forest. In India, Chilika Lake hosts about 156 Irrawaddy dolphins as of 2021. The riverine populations are considerably smaller and face the most severe threats.
In Cambodia’s Mekong River, the population was estimated at about 105 individuals as of 2024, showing some stabilization after previous declines. Myanmar’s Ayeyarwady River population is estimated to be between 59 and 72 dolphins. The Mahakam River in Indonesia harbors a population, with recent estimates suggesting around 70 individuals.
Major Threats
Irrawaddy dolphin populations face numerous threats. Entanglement in fishing nets, particularly gillnets, is a major cause of dolphin mortality. These nets can ensnare dolphins, leading to drowning or injury. For instance, two-thirds of dolphin deaths in Indonesia’s Mahakam River over 25 years were attributed to entanglement in fishing nets.
Habitat degradation is another significant threat. This includes pollution from various sources, such as pesticides and mercury from gold mining operations, which can suppress the dolphins’ immune systems and make them more susceptible to disease. Dam construction alters water flow and fragments habitats, while sand mining further destroys crucial areas. Overfishing of their prey reduces the food available to dolphins, impacting their survival and reproductive success. Increased boat traffic generates noise pollution and raises the risk of vessel collisions, disrupting dolphin behavior and displacing them from their habitats.
Conservation Initiatives
Various efforts are underway to protect Irrawaddy dolphins and their habitats. Establishing protected areas is a primary strategy, such as Myanmar’s Irrawaddy Dolphin Protected Area, which prohibits harmful fishing practices. Cambodia has also established the Mekong Irrawaddy Dolphin Management and Conservation Area. These protected zones aim to create safe havens for the dolphins and regulate human activities within their range.
Community-based conservation programs play a significant role, engaging local populations in protection efforts. This includes promoting sustainable fishing practices and offering alternative livelihoods to reduce reliance on methods that harm dolphins. For example, some projects encourage eco-tourism that provides incentives for dolphin conservation. Research on dolphin ecology, population dynamics, and mortality causes is ongoing; organizations conduct regular surveys and monitoring. Efforts also focus on reducing pollution and mitigating the impacts of dam construction and boat traffic.