IT LOVES warm, shallow tropical waters, whether salty or fresh, murky or clear. Its range covers an area from India’s Bay of Bengal through the Malay Archipelago to northern Australia.
Yet, few people—especially Australians, whose northern doorstep may hold the largest concentrations of this animal in the world—have ever seen or even heard of the Irrawaddy dolphin. Surprising? Yes and no.
In the 19th century, zoologist John Anderson saw schools of this bluish-gray dolphin, with its round, beakless head, in the Irrawaddy River in Myanmar (then Burma). He gave it the name Irrawaddy dolphin.
Why Rarely Seen
Irrawaddies thrive in hot and humid coastal, estuary, and river regions. Their home is often flanked by mud, mangroves, jungle, clouds of mosquitoes and, in places, even crocodiles—not the surroundings that attract humans.
The water in these areas is also generally murky, so the only time you would see a dolphin is when it briefly surfaces to breathe. Even then, it keeps a low profile. Little of its back appears, and its dorsal fin is small compared with that of other dolphins.
But in some places Irrawaddy dolphins are not such a rare sight. Fishermen and riverboat operators working the Irrawaddy River in Myanmar, and other rivers in the dolphin’s Asian domain, frequently see the animals hunting and cavorting far upstream, even squirting jets of water from their mouths like water fountains or figurines in a water garden.
In Australian waters, the Irrawaddies range along the west coast, around the top of the continent, and down the east coast. They are usually seen in groups numbering fewer than 6 but occasionally up to 15. Unlike their Asian kin, the down-under clan have never been known to mimic water fountains.
Is It a Dolphin?
Irrawaddies live near land and are slow swimmers compared with their more sprightly blue-water cousins. Yet, scientists have had difficulty studying them. Their uninviting domain is a key factor. However, live Irrawaddies have been studied in the Jaya Ancol Oceanarium, in Djakarta, Indonesia.
Because little is known about Irrawaddies, until recently biologists were unsure where they fit on the whale-dolphin family tree. Obviously, they have much in common with dolphins. Yet, in form, not color (they range from pale to dark bluish-gray), they could almost pass for a smaller version of the Arctic beluga whale, or white whale. Even their unusually flexible neck is much like that of the beluga. So, what are they—the equatorial equivalent of the beluga or a true dolphin?
One way to find out is to load a broad range of their anatomic and genetic features onto the measuring scales, so to speak, and see which way the scales tilt. The weight of evidence, it turns out, falls on the dolphin side of the scales.
The Little We Do Know
At birth, Irrawaddy calves are some three feet long and weigh about 26 pounds [12 kg]. Males grow to about nine feet [2.75 m], and females, just a little less. They may live 28 years.
Samples taken from the stomach of dead Irrawaddies reveal a diet of squid, shrimps, prawns, and fish—especially bottom-dwelling fish. Some scientists speculate that the Asian dolphins’ curious practice of squirting water from their mouth may help them to hunt fish in murky waters.
Like other dolphins, Irrawaddies emit distinct clicks. Dr. Peter Arnold, of the Museum of Tropical Queensland, told Awake! that “according to research done at the Jaya Ancol Oceanarium, the Irrawaddy dolphin may well use its clicks to echo-locate prey as other dolphins do.”
Does It Have a Future?
Scientists have no idea how many Irrawaddies there are in the world. But there is growing concern that they are under threat. In some parts of Southeast Asia, their numbers are in decline, and in other parts, they can no longer be found at all.
This is often due to logging operations and the associated pollution and silting of rivers. In Australia, much of the Irrawaddy’s territory remains relatively uninhabited by humans. But in the more attractive areas on the east coast, urbanization and tourism have taken their toll. Some Irrawaddies drown in fishing nets, and some, in shark nets set near beaches to protect swimmers. Overfishing of the Irrawaddies’ food supply also affects their numbers.
The greatest potential threat, though, may be the swelling tide of pollutants that wash into rivers and estuaries. Among the worst are synthetic organic compounds, such as polychlorinated biphenyls (PCBs), that tend to persist in the environment. PCBs have been used in electronic components, paints, lubricants, coatings for wood and metal, and other products.
On the positive side, the Australian Nature Conservation Agency, in their document The Action Plan for Australian Cetaceans, states: “Much of [the Irrawaddy dolphin’s] range in Queensland is covered by the Great Barrier Reef Marine Park; the possibilities for management in Queensland waters are therefore good.”
As another step toward better management, the agency recommends that along with the humpback whale, the southern right whale, and the bottle-nosed dolphin, the Irrawaddy be made a primary species in public awareness programs. That will be good for the Irrawaddy dolphin—and for us.