Over 120 Amazon dolphins, thousands of fish dead from suspected heat, drought

 October 7, 2023

A severe heat wave and drought in a tributary of the Amazon River may have caused the death of 120 endangered dolphins in the last week, along with thousands of fish.

Scientists working in the area suspect that the heat and lack of rain caused water temperatures to rise to unhealthy levels for the dolphins, many of which are distinctive pink dolphins. The fish died from a lack of oxygen in the water, which was caused by the rise in temperatures.

Biologists in protective gear retrieved some of the decomposing dolphin bodies to perform autopsies, looking to determine the exact cause of death.

In addition to the heat, a bacterial infection could have caused the deaths of the dolphins.

Global warming, of course

Of course, the scientists are blaming global warming for the deaths even though they haven't specifically confirmed as much yet.

The dolphins are relatively rare freshwater species, and their slow reproductive cycles make their extinction more of a threat.

The river water was 102 degrees Fahrenheit--more than 10 degrees warmer than normal--on Thursday when the first 70 dolphin bodies washed ashore. After a brief time when temperatures cooled off, they again surged to 99 degrees on Sunday.

Miriam Marmontel, a researcher at the Mamiraua environmental institute that focuses on the mid-Solimoes river basin, said that the deaths could represent 10% of the entire population of the species.

"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 Tefé," Marmontel said.

Saving the rest

Brazil's Chico Mendes Institute for Biodiversity Conservation quickly sent veterinarians and aquatic mammal experts to the area in an effort to save dolphins that are still alive in the nearby lake.

Unfortunately, they can't move the dolphins to a cooler area until they rule out a bacteriological cause to the deaths, since doing so could infect other wildlife and cause more deaths.

The pink dolphins, known as “boto," are the largest known dolphin species and can grow to nine feet long, according to the Aqua Expeditions website.

They are social creatures who often play with local children without displaying aggression, and their brain capacity is larger than normal--40% larger than human brains.

The vertebrae in their necks are unfused, which makes them more agile than other dolphins, but they usually remain mostly under the murky waters they live in, so scientists don't have a lot of information about them.

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