Vampire bats keep their social distance when ill

Vampire bat

Ironically, a study has found that vampire bats keep their social distance when ill in order to protect the group, despite the experts deciding that bats are the probable cause of the coronavirus pandemic. Of course it is humans who are the ultimate cause of the pandemic in allowing a zoonotic disease to be transmitted from a wild animal to humans.

Vampire bat

Vampire bat. Photo: WIKIMEDIA, DESMODUS

So although bats have been blamed for the coronavirus crisis they themselves behave in a very altruistic and sensible way when ill. They are an extremely sociable species and therefore good candidates to test their behaviour when ill. If they didn’t socially isolate a contagious disease would spread more rapidly throughout the group. They roost in sizeable groups and groom each other and even share food. They can switch between groups which would make it more likely that a disease would be transmitted.

In the latest study they injected bats with a substance which challenged their immune system and made them feel ill. The control bats were injected with saline solutions. They returned the bats to their group in a tree and tracked their behaviour.

They found that the unwell bats spent less time near others. They also associated with fewer mates in the group and accordingly were less socially connected to them.

Wild vampire bats that are sick spent less time near others from their community which slows how quickly a disease will spread. – Simon Ripperger, an evolutionary biologist and the study’s lead author.

Social distancing also occurs in finches, ants and lobsters as has been discovered in studies. I suspect it happens in other animals as well because it couldn’t just occur in ants and lobsters! Interestingly when spiny lobsters are sick they secrete a chemical in their urine which warns others to avoid them.

The study found that within four hours of becoming sick, bats associated with four fewer other bats on average than those bats that had been injected with a saline solution (the well ones). It seems, too, that the bats that weren’t sick avoided those that were sick. One average a “control bat” had a 49% chance of interacting with another control bat but this was reduced to 35% with respect to sick bats.

The sick bats also spent less time with other bats by cutting their interaction sessions down by 25 minutes. The study was able to collect data every few seconds to precisely monitor how the bats altered in behaviour during the time that they were sick and I presume when they felt better.