Oct. 31 (UPI) -- Vampire bats that hang out with each other in captivity, eating side-by-side and grooming one another, often stick together even after they're released into the wild.
Authors of a new study on the phenomenon, published Thursday in the journal Current Biology, suggest the bat's behavior is further proof that a diversity of mammal species can form and maintain friendship-like social relationships.
"The social relationships in vampire bats that we have been observing in captivity are pretty robust to changes in the social and physical environment -- even when our captive groups consist of a fairly random sample of bats from a wild colony," Simon Ripperger, researcher at the Leibniz-Institute for Evolution and Biodiversity Science in Germany, said in a news release. "When we released these bats back into their wild colony, they chose to associate with the same individuals that were their cooperation partners during their time in captivity."
Ripperger, who also conducts research at Berlin's Natural History Museum, worked with Gerald Carter of Ohio State University on the study. Though not all of the captive bats in the study maintained their partnerships in the wild, many did, suggesting the friendships were not simply the result of confinement.
According to Ripperger and Carter, the formation of bat relationships is similar to human friendships in that they're dictated by a combination of social preferences and external environment influences.
The ability to track social relations among wild bats was made possible by tiny proximity sensors that were developed by Ripperger's work with electrical engineering and computer science researchers. The sensors helped scientists map social networks of bats, as well as determine whether bats continued to spend time with the same bats outside of captivity.
When the researchers looked at who bats spent the most time with inside and outside of captivity, they found a strong correlation between feeding and grooming partners, especially among female bats.
Most research into social relations among animals has focused on primates, but a growing body of research suggests a wide array of species are capable of friendships.
"Our finding adds to a growing body of evidence that vampire bats form social bonds that are similar to the friendships we see in some primates," Carter said. "Studying animal relationships can be a source of inspiration and insight for understanding the stability of human friendships."