FunNature & AnimalWhy did some Bolivian dolphins swim with an anaconda?

Why did some Bolivian dolphins swim with an anaconda?

The case of Bolivian river dolphins that were interacting with a Beni anaconda, carrying it in their mouths in August last year, has been published in the journal Ecology and researchers have given different possible explanations for this unusual event.

River dolphins are relatively rare creatures, as they rarely stay with their heads above water for very long. Much more strange is that at the same time they carry an anaconda between their jaws . What is known is that dolphins and cetaceans in general carry out recreational activities. Other animals can participate in them, voluntarily or involuntarily.

The photo of the dolphins entertaining themselves with the snake was taken in August 2021, near the Tijamuchi River, in Bolivia. The researchers observed a group of dolphins that remained above the water longer than usual, but only after reviewing their images did they get a clearer idea of what could be happening.

“After reviewing the first images we realized that (the dolphins) were handling a snake and, although it was difficult to estimate the size of their group, there were at least six,” the researchers write in the Ecology article in which they describe the observation. . “It became clear that they were playing with the snake rather than trying to eat it .”

The dolphins interacted with the snake in different ways. One of them was occasionally swimming together in sync but staying mostly in the same area (the activity spread about 70-80 meters downstream as the researchers watched over the course of 7 minutes).

These interactions between dolphins are rare , and it’s possible the cetaceans were teaching each other about the snake, the researchers say, or perhaps eating it instead of playing with it. Another possibility is that the playful activity was actually sexual in nature .

Regarding the latter, the researchers wrote the following in the publication: “Subsequently, we could observe in the photographs that the adult males were sexually aroused while participating in object play with the anaconda.”

Another explanation given by the researchers is that the goal of the interaction could be to show the anaconda to the youngsters in the group, to teach them about the reptile. “There were also youngsters on the scene, and it appeared that the adults were displaying the snake to them,” the scientists write.

The Beni anaconda ( Eunectes beniensis ) can grow up to 2 meters in length and lives in the same part of the world as the Bolivian river dolphin ( Inia geoffrensis boliviensis ), specifically in the northeastern part of the Amazon rainforest in Bolivia. The Bolivian river dolphin draws attention to its totally pink skin. It has more teeth and is larger than I. Geoffrensis , a species of dolphin from which it was once believed to derive, it also has a smaller cranial cavity

River dolphins are often difficult to observe as rivers tend to be muddier and more difficult to navigate than oceans, so while the details of what has happened are not 100% clear, this is a very useful sample to have. It shows us how these cetaceans spend part of their time . Also taking into account that sadly they are in danger of extinction.

Of course, the experience most likely did not end well for the anaconda. It did not move during the interactions and remained underwater for a long time, leading researchers to believe that it probably died in the end.

“I don’t think the snake had a very good time,” one of the team members, biologist Steffen Reichle of Bolivia’s Noel Kempff Mercado Museum of Natural History, told the New York Times .



Entiauspe-Neto O, Reichle S, dos Rios A. 2022. A case of playful interaction between Bolivian River Dolphins with a Beni Anaconda. Ecology. DOI:

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