Vampire bats socially distance themselves when they are sick, according to a study published by Oxford University Press. The researchers found that vampire bats spend less time near others if they do not feel well, which slows disease transmission.
While the research team had previously observed this behavior in the lab, a field experiment has now confirmed that sick vampire bats self-isolate in the wild.
Social behavior can control how a virus spreads throughout a population, and parasites can increase their own spread by manipulating the behavior of their host. When animals are sick, they may isolate themselves voluntarily or be isolated by others. Infected animals may also simply reflect illness in their behavior by sleeping more and socializing less, which is a common form of social distancing that does not require cooperation.
The researchers designed an experiment to investigate how sickness affects relationships among vampire bats over time. Using high-resolution data, the team analyzed the behavior of 31 female vampire bats from a roost inside a hollow tree in Lamanai, Belize.
Half of the bats were infected with an immune-challenging substance, and the other half received saline injections. Over the next three days, the bats were released back into their hollow tree wearing proximity sensors.
The experts tracked changes in the associations among 16 “sick” bats and 15 control bats in their natural environment.
The bats that felt ill were found to associate with fewer individuals, spend less time with others, and were less socially connected to healthy bats.
During a period of six hours, the sick bats engaged with an average of four fewer members of the community compared to bats in the control group. The bats that felt under the weather also spent less time engaging with each individual by about 25 minutes.
Overall, the researchers discovered that the social networks among vampire bats are surprisingly dynamic.
“The sensors gave us an amazing new window into how the social behavior of these bats changed from hour to hour and even minute to minute during the course of the day and night, even while they are hidden in the darkness of a hollow tree,” said study lead author Simon Ripperger. “We’ve gone from collecting data every day to every few seconds.”
The study is published in the journal Behavioral Ecology.
By Chrissy Sexton, Earth.com Staff Writer