Vampire Bat Friendships Persist from the Lab to the Wild

Vampire bats form social bonds similar to those of primates.

Posted Oct 31, 2019

Photo by Oasalehm, via Wikimedia Commons. Distributed under a CC BY-SA 4.0 license.
Vampire bats (Desmodus rotundus).
Source: Photo by Oasalehm, via Wikimedia Commons. Distributed under a CC BY-SA 4.0 license.

In the wild, vampire bats form long-lasting social relationships with some of the individuals with whom they roost. These friendships — which can last a decade or longer — are built on mutual grooming, hanging around together, and sharing food.

Vampire bats (Desmodus rotundus) must obtain a blood meal every night in order to survive. If one comes back to the roost hungry, she can depend on a friend to regurgitate some of her meal. Vampire bat blood-sharing is a classic example of reciprocal altruism: helping another so they will help you out later.

Researchers studying this behavior in the lab found that putting bats into constant captive association made them more likely to share food. The researchers wondered if these relationships would last if the bats were back in the wild, where they could choose to go anywhere and associate with anyone, or if they were just an artifact of being in captivity.

 Sherri and Brock Fenton.
Tagged vampire bat in the wild.
Source: Photo: Sherri and Brock Fenton.

To find out, a team of biologists and engineers developed a new technology for tracking the social networks of wild bats. After living in captivity for almost two years, bats were released wearing miniature backpacks fitted with proximity sensors. These sensors, weighing less than a penny, logged social encounters every two seconds for more than a week. The resulting dataset gave researchers a new, high-resolution look at social bonds in wild vampire bats. They published their findings today in the journal Current Biology.

The data showed that bats that groomed and fed each other in captivity tended to maintain their social relationships by roosting together in the wild. Though not every relationship survived the transition from lab to the wild, most bats chose to associate with the same individuals with which they cooperated in the lab.

 Sherri and Brock Fenton.
Source: Photo: Sherri and Brock Fenton.

Similar to human experience, vampire bat friendships appear to grow from a combination of social preferences together with external circumstances. The findings underscore that living in close contact is important for building social relationships, but it’s not everything. For instance, think about all the people you befriended who lived in your college dorm. Some of those friendships may have lasted post-graduation, but others fade with distance.

The researchers are now looking at bats’ personality differences and manipulating their experiences in the lab to explore how individuals go from being strangers to socially bonded. What they learn could shed light on how other creatures, humans included, make and maintain friendships.

References

Ripperger SP, Carter GG, Duda N, et al. 2019. Vampire bats that cooperate in the lab maintain their social networks in the wild. Current Biology. DOI:10.1016/j.cub.2019.10.024.