…or, as some of us affectionately call them, the “waddies”.
Irrawaddy dolphins (Orcaella brevirostris) are a relatively little-studied species of dolphin that is distributed patchily around Southeast Asia. They occur in riverine, estuarine, and coastal habitat, which puts them in contact with a number of human activities. Though the species as a whole is listed as Vulnerable by the IUCN Red List, several subpopulations (i.e., geographically separated groups) are listed as Critically Endangered. Major threats include accidental entanglement in fishing gear, or “bycatch”, as well as habitat degradataion (particularly for the riverine subpopulations), pollution, and boat traffic.
Often, when asking fishers for information about local species, it can be hard to know what species of dolphin the fishers are referring to. The nice thing about working on Irrawaddy dolphins is that they have no elongated snout – they have stubby faces, unlike the other dolphin species that occur in the same areas. If I’m ever unsure if a fisher is referring to ‘waddies, I can just gesture: “They have a flat face, right? No snout?” That could cause some confusion with finless porpoises, but those are smaller, have no dorsal fin (as one would guess), and don’t overlap with the ‘waddies at three of my sites (and are rarely spotted at the fourth site, in Thailand).
In the sites where I’m working, locals even have a different name for these dolphins than they do for others. Sometimes, we even have to clarify that Irrawaddy dolphins are, in fact, related to other dolphins.
Their fragmented distribution makes them a fascinating species to study. Do their social and feeding behaviors differ between subpopulations? Do different subpopulations make different sounds? What are the different conservation threats and potential solutions for all of these subpopulations? They are closely related to the Snubfin dolphin (Orcaella heinsohni), which was only recently determined to be a different species and occurs in Australia and New Guinea.
We still have a lot to learn about this species, both in terms of basic biology, behavior, and ecology, and in terms of conservation. One population in the Philippines was only discovered to science in 2005! And researchers in Bangladesh only recently discovered that the population of Irrawaddy dolphins there was the largest known thus far, at about 6000 individuals. There might be more populations that remain to be discovered…