When you’re feeling sick, you probably aren’t that motivated to visit with friends and family—and the feeling is likely mutual. This is truer now than ever, with the current pandemic still going strong. Social distancing when we feel sick isn’t just something humans do, though. It turns out we share that sentiment with vampire bats. A team of ecologists at Ohio State University studied these bats in the wild and found that, when they’re feeling sick, vampire bats interact with fewer of their brethren and cut their social time short. The findings, led by Drs. Simon Ripperger and Gerald Carter, were published this fall in Behavioral Ecology.

From lobsters to birds, scientists have found that many animals will avoid sick members of their group. Scientists have even previously shown that sickly vampire bats are less socially connected, but they studied the animals in captivity. This latest study sought to check whether this trend translates to bat interactions in the wild. The ecologists traveled to Central America in search of a natural habitat housing a bat colony—and they found one: a hollow tree in Lamanai, Belize home to hundreds of common vampire bats. They captured a few dozen of them by casting nets over all but one of the exits from the large bat roost. Now that they have some bats, how can they make some of them sick for their experiment? With the chemical lipopolysaccharide (LPS), which makes mammals feel sick, i.e. lethargic and less active, without actually infecting them with some pathogen. They injected half the bats with LPS and the other half with saline that has no effect on them. As the final touch before being released back to their hollow tree home, they were all adorned with sensors that continuously record where they are relative to the other monitored bats.

As the study’s authors suspected, the sensors indicated that the sickly bats were socially isolated compared with the bats merely injected with saline. Sick bats associated with fewer bats, spent less time with each buddy, and were less connected to the more gregarious members of the colony—though it’s unclear how conscious the bats are of avoiding potential infection rather than just leaving their “sick” colony members to rest. In any case, the differences are not particularly dramatic, but they do demonstrate social distancing. Six hours after they were released back to their roost, healthy bats were 15% more likely to interact with each other than the “sick” bats. You might think this could just mean healthy bats are avoiding the sick ones—something humans certainly do. But “sick” bats were even less likely to spend time with each other than with healthy bats. Social distancing faded as the effects of the LPS injection wore off. Beyond demonstrating social distancing in sick vampire bats, the experiment’s success sets the stage for future wildlife studies that can use proximity sensors to study other animals in their natural home.

Like humans, bats are very social creatures. We understand that seeing other people when we feel ill could make them ill, too. These latest findings reinforce the idea that other animals may do the same—even if they don’t have public health experts telling them to do so.

Simon Ripperger is a poctdoctoral researcher at Ohio State University and a postdoc research fellow at the Smithsonian Tropical Research Institute in Panama. Gerald Carter is a professor of ecology at Ohio State University.

Managing Correspondent: Jordan Wilkerson

Original Science Article: Tracking sickness effects on social encounters via continuous proximity sensing in wild vampire bats

Image Credit: flickr

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