Cold-Blooded, but Not Cold-Hearted, Garter Snakes Form Friendships

By tracking 40 snakes over eight days, researchers found that the reptiles tended to return to the same groups

Eastern garter snake
Eastern garter snakes in the study stuck to their cliques and had a range of bold and shy personalities Public Domain

Garter snakes are some of the most common snakes in North America. As the weather warms up, they can be spotted slithering across lawns or sunning on rocks. Their range spans from Canada to Costa Rica, and new evidence suggests they don’t go it alone. Instead, garter snakes seem to form social bonds.

The research, published last month in the journal Behavioral Ecology and Sociobiology, looked at the behavior of 40 garter snakes—30 of them wild-caught, 10 captive-bred. When placed in an enclosure with a limited number of hiding places, the snakes not only formed groups, but returned to the same cliques after they were scrambled around. The findings match up with previous conclusions that reptiles can make friends and could be used to improve reptile relocation efforts.

“Social behaviors of reptiles generally—and snakes in particular—are more complex and likely meaningful than we had thought,” University of Florida ecologist Harvey Lillywhite, who wasn’t involved in the research, tells Elizabeth Pennisi at Science magazine. Lillywhite’s past research has shown that cottonmouth snakes socialize and forage in pairs.

Study leader and behavioral ecologist Morgan Skinner of Wilfrid Laurier University in Canada placed ten snakes at a time in a walled enclosure measuring about three feet per side. The enclosure had four boxes for the snakes to hide in, so for all of them to find shelter, they had to group up. Each snake sported a colorful dot on its head so the researchers could identify individuals in photos of the enclosure, which were taken every five seconds for eight days to track the snakes’ movements.

Twice per day, Skinner recorded what groups had formed.

“All animals—even snakes—need to interact with others,” Skinner tells Virginia Morell at National Geographic. “Like us, they seek out social contacts, and they’re choosy about whom they socialize with.”

The snakes formed groups of up to eight individuals. And when Skinner checked on the groupings, he removed the snakes from the enclosure, cleaned the space and put the snakes back in different places around the box. On camera, the researchers watched the snakes return to their previous cliques.

Their behaviors and social connections “are in some ways surprisingly similar to those of mammals, including humans,” Skinner tells Science magazine.

During the research, Skinner also conducted personality tests on the snakes, which placed them in one of two groups, either “bold” or “shy.” The simple categories are a common metric used in animal behavior studies today; dolphins have bold and shy personalities, too. In snakes, one serpent’s boldness was measured by how much time it spent exploring a new enclosure. Very bold snakes took time to see the sights and smell the air, while shy snakes were satisfied to sit inside their shelters. But the researchers also found that groups tended to act together, entering or leaving their hiding place at the same time regardless of personality type.

“It’s really cool to see this study,” says Melissa Amarello, herpetologist and director of Advocates for Snake Preservation, to National Geographic. But she adds, “animals behave differently in captivity, so I’m left wondering how this translates to natural conditions.”

Skinner and co-author Noam Miller, who is Skinner's adviser at Wilfrid Laurier University, tell National Geographic that wild garter snakes tend to group up in a similar way, so the behavior may translate beyond the lab. A group of cuddling snakes could conserve heat and moisture better than a lone serpent, and living in a group gives each snake better odds of escaping if the crew is attacked by a predator, Miller tells Science.

The cliquey behavior might also explain why reptiles often leave the areas that they’re relocated to for their own safety. Relocating might work better if the snake’s entire friend group is moved together. To top it off, treating their new home with the species’ scent could entice the crew to stay.

For Lillywhite, the new paper is “a significant beginning” to the study of social behavior in snakes, he tells Science.

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