Ecologists explain why Bolivian dolphins swim with anaconda in their mouths

Brazilian and Bolivian researchers photograph Bolivian river dolphins Inia geoffrensis boliviensisanaconda floating with me Eunectes beniensis in the mouth. This case describes a portal science alert containing a link to a scientific publication in a journal Ecology.

River dolphins are not seen as often as their marine counterparts, mainly because the river water is cloudy and it is difficult for them to keep their heads above water for long periods of time. In addition, these dolphins are on the verge of extinction. It was even more surprising to watch a performance where two dolphins simultaneously swung a predatory snake sandwiched between their jaws. While it’s unclear exactly what happens in this case, dolphins and marine mammals in general are known for their sometimes voluntary and sometimes unwittingly playful behavior, often involving other animals.

The photo was taken in August 2021 near the Tijamuchi River in Bolivia. The researchers found a group of dolphins that stayed above the water longer than usual, but only after viewing the photos did they get a complete picture of what was happening there. “After checking the first photos, we noticed that they were holding a snake in their jaws, and although the overall size of their group is difficult to estimate, there were at least six of them,” the researchers write in their paper. “It turned out that they were playing with the snake instead of trying to eat it.” While the researchers observed this 7-minute scene, the dolphins interacted with the snake in several different ways, sometimes swimming together simultaneously, but mostly staying in the same part of the river, actively moving only 70-80m downstream.

Such interactions between dolphins are rare, perhaps in this case the dolphins taught each other or the young how to deal with snakes. Another version is that this game activity is actually sexual in nature. “We were then able to determine from the photographs that adult males were sexually aroused while playing with the anaconda,” the researchers said. “Youngsters were also on the scene, and apparently the adults were showing them the caught snake.”

Anaconda Beni can grow up to 2 m and lives in approximately the same places as the Bolivian river dolphin – in the Amazon rainforest in northeastern Bolivia. Most likely, this “game” ended badly for the snake, since during its interaction with the dolphins it was under water for a long time, during which time it inevitably had to drown.