Biology: Vampire bats social distance when they get sick

Modesto Morganelli
Ottobre 29, 2020

Researchers gave 16 of the wild bats a safe injection that made their immune systems react as if they were sick, to see if their behaviour would change. The chance that the latter spent time with a group member was around 49 percent, while this percentage was much lower for sick bats: only 35 percent.

The COVID-19 pandemic has taught millions of people across the world at least one valuable lesson: the single most important thing that one can do to stave off the spread of an infectious disease is to practice social distancing. But when we're sick, it's common to withdraw a bit and stay in bed longer because we're exhausted.

"The sensors gave us an unbelievable new window into how the social behaviour of these bats changed from hour to hour and even minute to minute during the course of the day and night, even while they are hidden in the darkness of a hollow tree", said the study's lead author, Simon Ripperger.

For the study, the authors carried out a field experiment in order to ascertain the manner in which behavior during sickness can impact social relationships with time among the bats. For instance, the sick ants self-isolate while healthy ants reduce their interactions with their peers when they sense disease is present in the colony.

With what they learned from captive studies, Ripperger and colleagues traveled to Lamanai, Belize, to tag and track vampire bats in their native habitat. Among their previous findings: Vampire bats make friends through a gradual buildup of trust, and vampire bat moms maintained social connections to their offspring even when both felt sick.

Just six hours after the injection, a sick bat would on average associate with four fewer bats than those injected with the saline. In short, vampire bats also wear when they are sick social distancing.

The sick creatures associated with fewer group mates, spent less time with others, and were less socially connected to healthy group mates, they found.

"One reason that the sick vampire bats encountered fewer groupmates is simply because they were lethargic and moved around less", Carter said. We had previously studied this in the lab. Our goal here was to measure the outcomes of these sickness behaviors in a natural setting.

They spend less time around their conspecifics, which means that the disease is less likely to spread.

'As tracking technology improves the capacity to create dynamic animal social networks from large, high-resolution datasets, we expect researchers to gain new insights into the patterns and processes underlying the spread of pathogens, information, or behavioral states'. In addition, sick bats spent almost half an hour less time with others.

Scientists at Ohio State University tracked a group of wild bats living inside a hollow tree by fitting them with tiny backpack computers, all to find out how they interacted socially with each other.

This work was supported by the German Research Foundation and a National Geographic Society Research Grant.

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