Vampire bats bond after being randomly paired up

Humans are known to sometimes bond when paired randomly with others, such as with roommates or coworkers. New research published in the journal Biology Letters suggests the same is true of vampire bats.  

Study senior author Gerald Carter is a professor of Evolution, Ecology and Organismal Biology at Ohio State University. 

“The process of how social bonds form is this fundamentally mysterious thing that a lot of people are interested in, but have very different interpretations of how it happens,” said Carter. 

“We’re trying to build vampire bats as a system where we can directly test these interpretations. In this experiment, we forced them together for a short amount of time and then measured their grooming rates, which increased by a specific amount over a period of time. It just hasn’t really been done before.”

The researchers collected 21 bats from three distant roosts and placed them together in a new colony. Initially, all of these vampire bats were allowed to mingle as they saw fit and groom each other as they would. Then the scientists split the bats into smaller groups of three, each from a different site, now living together for seven days. These new groups formed internal bonds, Imram Razik, a graduate student at Ohio State explained,  

“From early on, they had potential to start grooming relationships, and then we did the forced proximity phase to see if we could increase the rates of grooming in random pairs. We then measured grooming during the post-treatment phase to compare pre- versus post-treatment grooming,” said Carter. 

Next, pairs of these bats that were forced to live together were observed and compared to both bats that weren’t forced to live together and came from separate colonies and those from the same colony that already knew each other. The researchers looked at grooming behavior of these different bat groups. 

The results, captured on infrared cameras, showed that the bats who were forced to live together groomed more often than the control or even bats who lived in the same colonies.     

“It was a striking pattern,” Carter said. “One thing you might imagine is that, after these bats are in their ‘college dorm room’ together, they stay together for a little while afterward but that quickly goes away – but we didn’t see that. The test bats were still grooming each other more than the control bats even at the end of the experiment, nine weeks later.”

The researchers compared this result to that of dormitory room mates, where two random people are paired together but then seek each other out later because of that pairing.

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By Zach Fitzner, Earth.com Staff Writer