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MANAUS (Reuters) – A team of biologists, veterinarians and fishermen captured rare freshwater dolphins in an Amazon lake this week to study their health in hopes of avoiding the deaths of hundreds of the mammals last year due to a severe drought.
After the researchers completed their work, which included inserting microchips to track the dolphins’ behavior via satellite, the dolphins were brought ashore for blood tests and other examinations and returned to Lake Tefe.
Fishermen were very careful not to harm the adult female dolphin during the capture process and kept her close to her offspring.
“She relaxed enough that we could do the tests. She seemed to be doing fine,” Marmontel said. The work included removing samples for biopsies and placing a microchip on her back that will allow researchers to track her movements, how deep she swims and even learn the water temperature remotely.
Last year, the Amazon rainforest suffered its longest drought on record, with more than 200 porpoises found dead in a lake formed by a tributary of the Amazon River.
Low river levels during the drought caused water temperatures to rise to levels that were unbearable for dolphins, researchers said. Thousands of fish in Amazon rivers also died due to a lack of oxygen in the water.
Amazon river dolphins, mostly bright pink, are a unique freshwater species found only in rivers in South America and are one of the few freshwater dolphin species left in the world. Their slow reproduction cycle makes their populations particularly vulnerable to threats.
“We will study the health of the dolphins before the dry season arrives so we can understand how they react to the heat,” said Miriam Marmontel, project leader at the Mamilaua Institute for Sustainable Development, which organized the expedition to capture up to 20 dolphins.
She said 300 dolphins died last year, most of them in Lake Tefe, a 45-kilometer-wide (27-mile) body of water next to the Solimois River that is a favorite haunt of the dolphins.
During the 2023 drought, the lake reached a temperature of 40.9 degrees Celsius (105.62 degrees Fahrenheit), more than 10 degrees above the average for that time of year. Currently, the lake is 30 degrees Celsius (86 degrees Fahrenheit), said Ayan Fleischmann, a researcher in geological sciences at the Mamilaua Institute.
Environmentalists blame the unusual conditions on climate change, which makes droughts and heat waves more likely and more severe. The role of global warming in last year’s Amazon drought is unclear, and other factors such as El Nino also played a role.
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