Although bats may have received more negative attention over the past year due to their suspected role in the spread of the novel coronavirus, new research shows that, like humans, vampire bats socially distance from one another when they are feeling unwell.
The study from Ohio State University, published in the journal Behavioural Ecology, administered a substance to 16 female wild vampire bats that made them feel sick for several hours, but did not cause disease. A further 15 female wild vampire bats received a saline placebo. The bats were then returned to their roost — a hallow tree in Lamanai, Belize.
Upon returning to their roost, researchers were able to record the animals’ social behaviour over the course of three days via custom-made ‘backpacks’ glued to the bats’ backs.
These contained proximity sensors weighing less than a penny, and designed to fall off the animals within a couple of weeks. The sensors recorded data every few seconds, enabling the scientists to analyse the bats’ social behaviour within the colony.
Data revealed that the bats who felt unwell interacted with fewer bats and spent less time near others. Healthy bats were also shown to be less likely to associate with a sick bat.
“Social distancing during the COVID-19 pandemic, when we feel fine, doesn't feel particularly normal,” explains the paper’s co-lead author, Simon Ripperger of Ohio State University.
“But when we're sick, it's common to withdraw a bit and stay in bed longer because we're exhausted. And that means we're likely to have fewer social encounters.
“That's the same thing we were observing in this study,” he continues. “In the wild, vampire bats — which are highly social animals — keep their distance when they're sick or living with sick groupmates. And it can be expected that they reduce the spread of disease as a result.”
Although the study didn’t document the spread of an actual disease as the scientists wanted to isolate the effect of the sickness behaviour, the findings can allow researchers to predict how sick animals’ behaviour can influence the spread of a pathogen in a social network.
"The effects we showed here are probably common in many other animals,” says Gerald Carter, co-lead author and assistant professor of evolution, ecology, and organismal biology at Ohio State University.
But he urges caution in reading into the results of the study, which did not use a real pathogen: “[It] is important to remember that changes in behaviour also depend on the pathogen," he explains.
"Some real diseases might make interactions more likely, not less, or they might lead to sick bats being avoided."