A New Species of River Dolphin Is the First to be Discovered in 100 Years

After recent reports of getting high and raping each other to show their dominance, dolphins are making the news again, only this time for more endearing reasons.

For the first time in nearly a century (the last discovery was in 1918), scientists have discovered a new species of dolphin in the Amazon River. It was previously thought only two species of river dolphin lived there, but research published in the journal PLOS One has shown that there are actually three, and the most recently discovered one should immediately be given ‘endangered’ status.

The species has been given the scientific name Inia araguaiaensis after the Araguaia River Basin where the scientists discovered it, but thankfully also has a common name that's less of a tongue twister, the Araguaian boto.

The discovery was rather unexpected. While conducting research, scientists from the Federal University of Amazonas in Brazil were not surprised to see a group of dolphins in a basin of the Amazon river—two species of “boto” (the name given to river-dwelling dolphins) were known to inhabit the region—but they noticed that one particular group was separated from the others by a small series of rapids and a canal. This led them to suspect that the group they had come across might be a distinct species.

The team, led by Tomas Hrbek, conducted in-depth DNA tests to study sections of the nuclear and mitochondrial DNA from the three separate species. Their findings indicated that the newly discovered species indeed evolved separately from the previously known types, and hasn't been interbreeding with them.

Further tests comparing male and female Araguaian botos with males and females from the two previously known species found small differences in the number and shape of their teeth and skulls (the Araguaian dolphins’ skulls were slightly wider). All of this evidence combined led the scientists to hypothesise that the “individuals from the Araguaia River represent a distinct biological group”, which most likely separated from other dolphin species over two million years ago.

Despite killing dolphins being taboo among locals in the Amazon Basin, they're among the rarest animals in the world. Three of the four previously known species are on the IUCN Red List, defined as being “threatened.” Threats they face include hydroelectric dams, excessive boat traffic and pollution, which all contribute to their habitat loss. Overfishing is also a risk, and directly depletes their population as well as their food supply.

The lead scientist of the study, Tomas Hrbek, told Science that, “based on census data there are probably only a thousand individuals, which is a very small population size," and added, “It’s not a very rosy picture”. For this reason the researchers only conducted research such as the skull and tooth measurements on a few specimens; it’s very difficult to find dead animals, particularly among such a small population size.

The very small number of Araguaian botos means that, while the discovery is exciting for the scientific community, it’s also worrying for conservationists. Scott Baker, a conservation geneticist at Oregon State University, examined the findings and told Science that because the Araguaian dolphin is a distinct species and doesn't interbreed with the rest, “the loss of any one of them is not replaceable”.