One of the team, biologist Stephen Reichel, of the Noel Kempf Mercado Museum of Natural History in Santa Cruz de la Sierra, Bolivia, commented that just seeing dolphins with their heads above the surface was truly extraordinary. Scientists noticed something unusual was happening and started taking pictures.
And only after taking a closer look at the team’s photos, scientists realized that porpoises were swimming with anacondas hanging from their mouths.
The researchers described what they saw in the journal Ecology last month. Dolphins living in captivity and in the wild are notorious for being playful, but the surprising behavior of Bolivian whales appears to have reached new levels of play among aquatic mammals, and some scientists are still not sure how to explain what the team observed.
Bolivian porpoises usually swim below the surface, Rachel said, to the point where only the fin or tail is usually seen. But some of the six animals they saw kept their heads above the murky waters of the river for an unusual amount of time.
At one point, male porpoises appeared swimming synchronously, holding a rattlesnake in their mouths. Anacondas are semi-aquatic snakes and can hold their breath for some time. But since this anaconda was handled by porpoises for at least seven minutes, and was submerged for most of that time, it likely died.
“I don’t think the snake had much fun,” Rachel said.
Because of the long duration of the interaction, scientists believe it was a game rather than a predator. The Bolivian anaconda is a super predator. With the exception of one case of cannibalism, scientists have never documented the occasions when this snake was eaten. In this case, the scientists did not see what happened to the anaconda.
Taxonomist Omar Antiausby Neto from the Federal University of Rio Grande do Sul And one of the authors of the article.
Some of the dolphins collected were young, a fact that may indicate another dimension of interaction: the adults could teach the young about anacondas or show them a hunting technique.
But behavioral ecologist Sonia Wilde of the Max Planck Institute for Animal Behavior in Germany, who was not involved in the study, doubted that the interaction was intentionally indicative. To her, the little porpoises were likely watching because they were curious.
Since anacondas are powerful, Wilde hypothesized that the snake might have been injured or dead when it was captured by porpoises. Of all the things a dolphin can put in its mouth, she said, “this seems rather unusual.”
“This is the first time I’ve heard of dolphins playing with a large snake,” added Wilde, who has observed bottlenose dolphins using shells as tools.
Another thing visible in the photos caught our eye: the erect penis of male porpoises.
It may have aroused them sexually,” said Diana Reese, a marine mammalian and cognitive psychologist at Hunter College in Hunter City. New Yorkwho did not participate in the study. “It could have been something they could touch.”
The excited males could have played a sexual joke on each other when the snake got entangled.
Scientists who study dolphins are familiar with animals’ sexual preferences, such as rubbing their genitals with toys or inserting their penises into moving or rigid objects. According to Reese, they often use the penis for tactile interactions. I noticed a male bottlenose dolphin trying to pierce the vent of a pilot whale that had been rescued from an aquarium. He added that it is possible that the males tried to insert their penis into the snake.
“There are a lot of questions,” said Entiaospi Neto.
Much more is known about marine dolphins than freshwater dolphins, or porpoises, in part because it is difficult to see what happens when river waters are cloudy. For Reese, although limited in nature, “These observations are always valuable. They give us another glimpse into the lives of these animals, especially their lives in the wild.”
Whatever happens in this animal encounter, it’s not the kind that appears in children’s books.
Translated by Clara Allen.