Amazon River’s Pink and Grey Dolphins Are Dying

The carcasses of 120 river dolphins – the famous pink river dolphins (called “boto” in Brazil) as well as the grey river dolphins (called “tucuxi”) – have been found floating in a tributary of the Amazon River in Brazil since last week in circumstances that experts suspect were caused by severe drought and heat.

The scientists are working to rule out other causes, such as a bacterial infection that could have killed the dolphins. But at least 70 of the carcasses surfaced late last week when the temperature of Lake Tefe’s water reached 39C (102F), more than 10 degrees higher than the average for this time of the year. 

A research group at Brazil’s Ministry of Science, Technology and Innovation, the Instituto de Desenvolvimento Sustentável Mamirauá in Tefé, western Brazilian Amazon, said two more dead dolphins were found on Monday in the region around Tefe Lake, an ecological hotspot for freshwater life in the Brazilian Amazon. 

Video provided by the institute showed vultures picking at dolphin carcasses washed up on the lakeside, while local media report thousands of fish have also died. 

Experts are now warning that many more dolphins are also at risk of death, if the water in the region's lakes doesn't cool down soon. The Brazilian government last week sent teams of veterinarians and aquatic mammal experts to investigate the deaths.

Miriam Marmontel (right), a researcher at the said institute said roughly eight of every 10 carcasses being found are pink dolphins and could represent 10 percent of their estimated population in Lake Tefe.

“Ten percent is a very high percentage of loss, and the possibility that it will increase could threaten the survival of the species in Lake Tefe”, she said. 

Note: The Amazon river dolphin, more popularly known as pink river dolphin (Scientific name: Inia geoffrensis) is different from the grey river dolphin (Scientific name: Sotalia fluviatilis) in that it bears more resemblance to the marine dolphin with its bottlenose and habit of leaping out of the water. And as its name suggests, the pink river dolphin is most recognizable by its unique color. Both are freshwater dolphins and are on the International Union for Conservation of Nature’s red list of threatened species. 

Ayan Fleischmann, the Mamirauá Institute's geospatial co-ordinator,  said the drought had also had a major effect on the riverside communities in the Amazon region, with some more isolated communities unable to be reached due to rivers drying up.