The Reason Sick Vampire Bats Self-Isolate


Vampire bats are typically social animals. They call to each other when away from the group. However, when they are sick, they tend to mix less with family and friends, according to a new study. One researcher said this was just like the reaction of humans.

These bats are friendly and social, at least with one another, grooming each other and sharing their questionably appetizing food supplies, which tend to be regurgitated mammal blood. We might see them as flying, bloodsucking creatures with vicious little teeth, but they are actually very social and friendly when with their own kind.

A sick vampire bat, however, will not interact so much with friends and family, and will call out less often, according to the latest research. We might call this behavior ‘social distancing’ – one of 2020’s buzzword terms. Is this intentional or not though? When we feel ill, we tend to want to hide away and recover rather than spent time in noisy, busy environments.

The researchers believe the same is true of bats. If they feel ill, they have less energy. They are not interested in social interactions when they are sick and feeling bad, explains Sebastian Stockmaier, one of the University of Texas’s doctoral candidates. According to Stockmaier and his colleagues, just like all sick humans want to do is stay in bed away from others, this same miserable lethargy makes bats act accordingly.

Under the weather vampire bats will call out 30% less frequently on average than healthy ones. Whether or not this is intentional, resting and keeping away from others certainly decreases the chances of disease transmission. Sick bats do not groom others so much, which will also reduce contagion.

The scientists visited Panama’s Smithsonian Tropical Research Institute to measure this. There are plenty of vampire bats in this region, as well as around various parts of South and Central America. The bats feed off the blood of horses, cattle and other mammals.

Vampire bats, with their long, pointed teeth, might be an unwelcome sight for many people, but Mr Stockmaier refers to them as ‘cute’, also explaining he finds them fascinating animals to study.

If you know where to get blood, you can easily find, catch and keep the bats in captivity, explains Stockmaier, who gets the blood from local slaughterhouses.

The experiment involved 18 female bats being injected with lipopolysaccharide (LPS). This compound produces an immune response like a bacterial infection, without actually causing the illness. It can last for between 24 and 48 hours. Females were chosen for this experiment because they tend to be more sociable than the males, spending more time feeding and grooming, as well as maintaining bonds with their offspring.

A saline solution was injected afterward as a control. The bats were removed from the group but still within hearing distance. Their calls were measured and recorded. The bats made 30% fewer calls on average. 15 of the 18 recorded fewer calls than the other 3 in the group.

A similar study showed the LPS-injected bats slept more, moved less, groomed less socially and produced other sickness symptoms. According to previous studies, similar animals need 8 times as much energy to call out than not to call out.

The conclusion is that bats are just feeling too miserable to call out, rather than deliberately self-isolating to prevent disease transmission to the others. ‘Bats are getting bad press right now,’ explains Stockmaier, because it is believed that Covid-19 originally came from horseshoe bats. He points out that this is a completely different species from vampire bats.