Even Bats Practise Social Distancing, Study Shows

A new study found that wild vampire bats that are sick, spend less time hanging out with other bats in their community. Indeed, this slows disease transmission throughout the community. We might learn a thing or two from our enemy's enemy, huh?

The premise of the research was that, in a lab setting, bats who have fallen ill showed similar behavior. So the team wanted to confirm it in a field study.

Sometimes parasites and pathogens change the host's behavior for their benefit. For example, malaria which is usually transmitted via mosquito bites can cause other mosquitoes to be attracted to you, speeding up the spreading process. Or Toxoplasma gondii, which is generally transmitted by cats, rewires the brain of its host to inhibit fear response and even cause a feeling of... sexual thrill? What's more interesting is that about 30 to 50% of the human population carries this parasite, but that's a topic for another article. And let's not even get started with the zombifying fungus. Nature is one hell of a nightmare fuel indeed. 

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Luckily, not all diseases and parasites can pull off this kind of menacing feats. Most diseases actually cause people and animals to be lethargic and sleepy, and in turn, less active and social.

Think about it, do you feel the compulsion to go out there socialize when you have a clogging upper airway disease? Certain eusocial insect species also show similar behavior, with either the sick ones self-isolating with their own will or with their fellow colonists avoiding them. So kudos to insects, their social distancing does not need cooperation, unlike us.

The method of study

To conduct their study, researchers captured and tagged 31 adult female vampire bats with high-resolution proximity sensors. They picked bats living inside a hollow tree in Lamanai, Belize.

Of course, the researchers didn't pick a sick intern and made them cough on the bats, what they did was injecting them with a type of lipopolysaccharide — this group of molecules is also known as endotoxins — which are usually found on the outer surface of gram-negative bacteria. While 16 of the bats got this injection, the remaining 15 were given a saline solution shot.

After this was done, they were let back to their hollow tree. Over the following three days, researchers recorded data from the proximity sensors. Compared to bats in the control group, the "sick" bats associated with fewer of their fellow trunkmates, and with the ones they associated with, they spent less time. All in all, the "sick" group was socially less connected to healthy ones, both directly and indirectly. 

In a 6 hour period, a "sick" bat associated with four fewer individuals of their community compared to a control bat. Control bats had an average of 49% chance to associate with any given bat but a 35% chance to associate with a "sick" bat. Sick bats also spent 25 minutes less with each bat on average. These differences became less pronounced when bats were sleeping or foraging outside their trunk. These differences also receded slowly as test bats "recovered".

So yeah, we could apparently learn a thing or two from these less-than-revered animals. 

The paper is published in Behavioral Ecology.