Snakes should be good at social distancing, at least according to what we know about reptiles: Most are solitary creatures that come together to mate and hibernate, but not much else. Not so garter snakes, the harmless serpents that live throughout North America and part of Central America. Researchers have discovered that garter snakes not only prefer to hang out together, but also seem to have "friends" with whom they spend much of their time.
"Snakes are really difficult to study due to their secretive nature," says University of Witwatersrand herpetologist Graham Alexander, who was not involved with the research. This new study and others, he adds, are lifting that veil of secrecy and "revealing snakes to be cognitive beings."
To learn how socializing affects individual animals, comparative psychologist Noam Miller and his graduate student Morgan Skinner at Wilfrid Laurier University have started to study a wide range of species, figuring that different animals may have different ways of interacting in groups. Because few researchers had looked at snakes, Skinner decided to test 40 young eastern garter snakes (Thamnophis sirtalis sirtalis) to assess their personalities and social preferences.
He placed sets of 10 snakes, each with a colored dot on its head, in a walled enclosure less than 1 meter per side. A camera kept track of the snakes' movements. Twice a day, Skinner photographed the snakes' groupings, removed the reptiles, cleaned the enclosure to erase any odors, and put the snakes back in different positions. The cameras then tracked whether the same groups re-formed.
They did, with snakes gathering in groups of three to eight in one of the enclosure's four shelters—small boxes, with a forward-facing opening. Those groups often consisted of the same individuals, suggesting the snakes form cliques, Skinner and Miller reported last month in Behavioral Ecology and Sociobiology. Their social structures "are in some ways surprisingly similar to those of mammals, including humans," Skinner says.
Skinner and Miller also tested each snake's personality. They measured a snake's "boldness" by putting it alone in a shelter. They then measured the amount of time the snake spent outside the safety of the shelter. Some were bold—spending a lot of time exploring the enclosure—and others were shy and stuck to the shelter.
When the snakes were in a group, they tended to do what the group did, regardless of their own personality. Overall, snakes spent about 94% of the time in a shelter. Animals with more snakes in their shelter were less likely to leave.
There are benefits to being social, particularly for younger snakes, Miller explains. For instance, a group retains heat and moisture better than an individual. Also, if a predator attacks, each individual in a group has a better chance to get away than one that is alone. Snakes can also get information from one another—when one snake sees another out exploring, it gets the signal that it's safe to go out, for example.
There have been other hints of social behavior in snakes. Harvey Lillywhite, a physiological ecologist at the University of Florida, and his students have noticed male and female cottonmouth snakes pairing off for long periods and foraging together. Pit vipers and African pythons care for their young. Herpetologist Melissa Amarello, executive director of the nonprofit Advocates for Snake Preservation, has observed communal dens and parental care in rattlesnakes. "Social behavior is not limited to a single site, single species, or even [single] family of snakes," she says.
Lillywhite cautions that the new results might not hold true in the wild, and that they might even have been different had a different enclosure design been used. Nevertheless, he says, the results are "a significant beginning," adding, "social behaviors of reptiles generally—and snakes in particular—are more complex and likely meaningful than we had thought."
Knowing that snakes have comrades, Miller says, could help efforts in their conservation: Often species that are relocated to safe habitats leave, frustrating conservationists. But if they know snakes prefer to hang out in groups, transferring whole groups or pretreating a new location with the species' scents might encourage the transplants to stick around the new location.