New research indicates that bats instinctively demonstrate their type of social distancing activities when they feel sick, just like what almost everyone is doing to slow the spread of COVID-19.
Scientists have been marking a group of wild vampire bats in Lamanai, Belize. They had been monitoring their social interactions every few seconds over a few days.
According to the team, the 'sick' bats distinctly changed their actions and were less friendly as they infected the bats with a drug that activated their immune systems.
"In the wild, [we observed] vampire bats - which are highly social animals - keep their distance when they're sick or living with sick groupmates," said Simon Ripperger, a bat researcher from The Ohio State University.
Ripperger added social distancing could reduce the spread of disease as a result.
Sickness Behavior
Previous study from this research community has shown that sick bats sleep more, walk less, expend less time grooming other bats in captivity, and make less social calls (usually finding their mates) in captivity. Experts call it 'sickness behavior.'
"We wanted to see whether these behavioral changes also occur in a natural setting where the bats are within their natural social and physical environment," Ripperger told ScienceAlert.
Collecting data on social connections between bats may help researchers understand how disease activity will minimize the spread of disease in these species, much as social distance does in humans.
So the researchers examined data from the colony roosting within a hollow tree from a narrowly caught party of 31 typical vampire bats (Desmodus rotundus), who are native to Latin America.
A drug to stimulate their immune system was inserted into sixteen randomly chosen female bats, making them feel ill for a few hours but did not cause any actual disease. Around 15 bats received a shot of salty water as a placebo.
They still had little sensors, each weighing less than a penny, glued to their small fuzzy backs until the 'sick' and stable bats returned to base.
Ripperger said the sensors provided us the ability to instantly observe an entire social community's actions, rather than focal sample individuals at a time, what one usually does in a laboratory environment.
How they tested the bats
Crafted by Ripperger and his team, the custom sensors operate by transmitting a signal every 2 seconds that wakes up any nearby sensors within 5 to 10 meters (attached to a bat).
The sensors logged an experience every time this occurred three days after the bats were caught and released. The scientists could tell from the frequency and length of the pairwise signal when two bats come into direct touch with each other and for how long.
Ohio State University behavioral ecologist Gerald Carter said they focused on three indicators of the ill bats' actions.
They noted how many other bats they met, how much overall time they spent with them, and how well-connected they were to the whole social network.
The network's study reveals that 'sick' bats were "emotionally disconnected" to their safe, social roost friends.
A 'sick' bat had four fewer interactions on average in the first six-hour span following care than a control bat, and 'sick' bats spent less time (25 minutes less) engaging with each mate.
As predicted, they largely resumed their usual social activity 48 hours later, after the medication had worn off and the 'sick' bats felt fine.
Other Challenges
Since the researchers could not inject the vampire bats with a true virus or bacteria, they could not test the propagation of an existing infection in a bats community, which may change bats' actions in other aspects.
Carter noted that shifts in behavior often rely on the pathogen. He added that any actual illnesses could make encounters more possible or contribute to the avoidance of sick bats.
Also, the analysis looked only at a specific number of bats inside a single roost.
It would be a greater challenge to monitor how bats migrate and communicate between colonies, particularly when scientists are now discovering the enormous distances that bats travel between roosts, including thousands of kilometers per year.
Researchers published the results in Behavioral Ecology.
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