Paddling a canoe down a murky river in Belize at the crack of dawn, Don McKnight and Jaren Serano listened for the sound of the Central American river turtle—locally known as a hicatee.

A hydrophone placed in the water detected movements of the reptiles, which had sonic transmitters attached to their shells.

The results floored them: The turtles were swimming around the river together, in some cases never straying three feet from a fellow animal. "It felt like I was tracking a pod of whales," says McKnight, an ecologist at LaTrobe University in Australia and the Belize Turtle Ecology Lab.

These social turtles may flip on its back what we think about the supposedly solitary animals, he says. It was previously thought that turtles will gather when they’re seeking the same resource, such as a sunny rock, but generally do not interact with one another.

In the recent research, however, the turtles seemed to seek out companionship. “It was wholesome to see,” says Serano, a master’s student at the University of Florida’s Department of Wildlife Ecology and Conservation. (Read: We thought we knew about turtles. A new discovery raises a mystery.)

What’s more, the scientists’ study, published this week in the journal Animal Behaviour, may help conservationists protect the critically endangered species, which has declined throughout its range of Belize, Mexico, and Guatemala. There are no solid population estimates of the heavily poached reptile, but their numbers could be as low as 10,000.

Hicatees are often sold on the black market for their meat, considered a delicacy in Central America. 

“Belize remains the last stronghold for the species, though with continued poaching for meat and eggs beyond household consumption, [it could go] extinct in the next 30 years,” says Venetia S. Briggs-Gonzalez, a wildlife ecologist at the University of Florida not involved in the research.

Random, or social?

McKnight and Serano were conducting other research on hicatees in spring 2020 when they discovered the animals move in unison.

"It's one of those random, dumb ways that science happens sometimes," McKnight says.

To find out if the turtles were really socializing, the team then found a section of river that had none of the known variables that might attract turtles, such as logs, rocks, or vegetation. By outfitting sonic transmitters to the shells of 19 juveniles of both sexes, the team could also rule out mating behavior.

The scientists then tracked the tagged turtles from a canoe daily for a few months, going up and down the river and measuring clusters of two or more turtles, which revealed distances between individuals. (See 17 cute pictures of turtles from National Geographic’s Photo Ark.)

It wasn’t easy. One day, the pair met a crocodile edging beside the canoe. During one massive downpour, they had to stop their work to bail water out of their boat.

Once the data was in, McKnight, Serano, and colleagues ran simulations to determine if the groupings and travel habits of the turtles were random or evidence of sociality. The randomized model showed the distances between turtles were always larger than what they found in the wild.

That means that real-life turtles were not moving at random—they were moving together in herds on purpose, in a variety of group sizes.

Unappreciated social lives

"There's probably a lot more social behavior going on than we were able to document," says McKnight, who hopes that his study will inspire more research into social reptiles, as the cold-blooded animals have largely been neglected in favor of mammals and birds. (Read how snakes have friends, too.)

"The findings will surprise some, but not those of us who have been studying social behavior in turtles,” J. Sean Doody, assistant professor in conservation biology at the University of South Florida, says in an email. He adds he’s seen similar behavior in pig-nosed turtles in tropical Australia but hasn’t yet documented it scientifically.

Doody, who wasn't part of the research, says it “dares to consider that turtles, ancient reptiles that predate humans by hundreds of millions of years, can have complex social lives other than courtship and mating or fighting.”

Adds Briggs-Gonzales, "there is a lot more about social behavior in the animal kingdom that we can fathom.”

A conservation boost?

It's also still unclear why turtles form groups, though it may be safety in numbers from predatory crocodiles, McKnight says.

And while crocodiles may be less likely to attack a bevy of turtles, poachers prefer it.

"The strategy they've [likely] evolved for most predators that's worked great for them backfires when it comes to humans," McKnight says. "We've always heard these reports from poachers that they're catching dozens of turtles in a night, which was really hard for us to understand," McKnight says. (Learn more about Earth’s freshwater species—and their struggles.)

This finding could also prompt a revision of existing laws in Belize, such as a crackdown on the use of gill nets, which can snag large groups of turtles at once, says co-author Day Ligon, a biology professor at Missouri State University.

Such efforts could prevent another tragic extinction, the experts agree.

“We don't want to lose this species like we did others that cluster together,” says Doody, “for example the passenger pigeon, which went extinct over a hundred years ago."