A team of biologists in Brazil has discovered a new species of river dolphin in the country's Araguaia River basin — the first such discovery in almost 100 years.
The researchers, led by Tomas Hrbek from the Federal University of Amazonas, believe there are only about 1,000 of the creatures alive, and that they separated from another South American species just over two million years ago. The team reported their results this week in the journal Plos One.
River dolphins are among the rarest of all water-dwelling mammals. The International Union for Conservation of Nature lists four existing species, three of which are on its Red List of threatened species. China's Yangtze river dolphin is believed to have gone extinct in 2006. Unlike the distantly related ocean-dwelling dolphins, river dolphins have long thin beaks which allow them to hunt for fish in muddy river bottoms.
The newest species was found in an area where sightings of the related Amazon river dolphin are relatively common.
"It was something that was very unexpected, it is an area where people see [river dolphins] all the time," lead author Dr. Tomas Hrbek told BBC. "They are a large mammal, the thing is nobody really looked. It is very exciting."
To determine whether they were truly looking at a new species, the researchers compared DNA samples from dozens of dolphins from both groups. They also compared the skeletons of a smaller number of specimens, and found the new species tended to have wider skulls and jaws. They suggested the species be named “Araguaian boto" (boto is the common regional name given to river dolphins).
In the paper, the researchers take care to highlight the conservation difficulties faced by the new species, which appears to have little genetic diversity.
"Since the 1960s the Araguaia River basin has been experiencing significant anthropogenic pressure via agricultural and ranching activities, and the construction of hydroelectric dams," they write. All this activity can have serious consequnces for the species that inhabit the river, they warn, suggesting the Araguaian boto be classified as vulnerable on the Red List.
In other dolphin-related news, Japanese fishermen drew international condemnation earlier this week when it was revealed that they'd killed 40 oceanic dolphins for meat. The annual hunt was the subject of the Academy Award-winning 2009 film The Cove, whose director Ric O'Barry spoke to George in 2012: