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It turns out that humans aren鈥檛 the only species that practices social distancing in response to infectious diseases. Two new studies have revealed that vampire bats become socially and physically isolated from other colony members when they feel ill.

鈥淰ampire bats are extremely social,鈥� says Sebastian Stockmaier at the University of Texas at Austin. These bats form strong ties not only with their kin, he says, but also with other members of their colony, building relationships through grooming and food-sharing.

Stockmaier and his colleagues were interested in how these relationships might be affected by disease, so they simulated this process in captive colonies of common vampire bats (Desmodus rotundus) in Panama. They injected some bats with a component of bacterial cell walls called lipopolysaccharide (LPS) that induces an immune response, making the bats feel and act ill.

The researchers then recorded the calls that the bats make for initiating social contact and facilitating physical interactions, comparing their frequency between those who had been injected with LPS and those who hadn鈥檛 . In a separate study, the same researchers tracked grooming and food-sharing between LPS-injected bats and their colony mates.

They found that the bats that felt ill made 30 per cent fewer contact calls than their healthy-feeling counterparts. The bats that felt ill were also more physically isolated from colony members, though there were exceptions. In general, LPS-injected bats both gave and received less grooming from unrelated bats, but mothers that felt ill still groomed their offspring, who returned the favour even if they felt ill too.

These priorities make sense to Krista Patriquin at the University of Toronto Mississauga in Canada, who wasn鈥檛 involved in this research.

鈥淚f you鈥檙e going to help anybody, you鈥檙e going to help your own offspring, and the risks of not helping them maybe outweigh the risks of potentially getting them sick,鈥� she says.

The researchers didn鈥檛 find any effect of illness on food-sharing, possibly because it is so immediately essential for survival, says Stockmaier.

While the bats鈥� social distancing could possibly limit a pathogen鈥檚 spread, Stockmaier doesn鈥檛 think these isolating behaviours have evolved to protect other bats. Instead, he says they may be a consequence of the bats鈥� malaise and lethargy from feeling ill.

Aside from humans, self-isolation for group survival has only been documented in colonial insects, such as ants, says Stockmaier. But other animals will distance themselves from ill individuals to save their own hides. Frog tadpoles avoid those infected with a pathogenic fungus, and mandrill monkeys can sniff out and avoid group members harbouring parasites.

Patriquin is curious about the lasting effects of bats that had withdrawn while ill on their聽social network. After all, bats don鈥檛 have videoconferencing tools for remote upkeep of relationships.

鈥淚s [the bat] maybe not going to get [groomed by others] as much, or is it not going to get fed as much after it鈥檚 been away for a bit?,鈥� she says.

Going forward, Stockmaier wants to investigate how the pathogens in naturally occurring infections, such as rabies or Bartonella,聽might impact bat social behaviour.

鈥淢aybe [the pathogens] wouldn鈥檛 decrease social interactions, or even increase them to favour their transmission,鈥� he says.