During a study with captive vampire bats at the Smithsonian Tropical Research Institute (STRI) in Panama, a young vampire bat pup was adopted by an unrelated female after its mother died. Although this observation was not the first report of adoption in vampire bats, it is uniquely contextualized by more than 100 days of surveillance-camera footage. This footage reveals intimate details about the changing social relationships between the mother, the pup and the adoptive mother throughout their time in captivity.
“The adoption took place after a very sad but ultimately serendipitous occurrence. We realized after the mother died and the other female stepped in to adopt the baby, that we had recorded the entire social history of these two adult female bats who met for the first time in captivity. The strong relationship they formed based on grooming and sharing food with each other may have motivated this adoption.”
-Imran Razik, short-term fellow at STRI and doctoral student, Ohio State University
To learn more about how vampire bats form social bonds, researchers captured vampire bats from three sites across Panama. These sites were all very distant from one another, such that bats from different sites were unrelated and had never met before. Their new home, a cage shrouded in black mesh fabric, was fitted with three infrared surveillance cameras that each recorded about six hours of footage every day for four months.
Based on the footage, bats that were initially strangers began to form new social bonds, which are best defined by grooming and food-sharing interactions. Grooming other individuals is somewhat common, whereas food sharing is less common, especially among strangers.
Vampire bats must eat often to survive — typically every night. If a bat is unable to find a blood meal, it may receive regurgitated blood from a close social partner.
“We wanted to see how these grooming and food-sharing relationships were forming, so we kept track of all grooming and food-sharing interactions on the video recordings.”
When the mother bat, Lilith, unexpectedly died and her 19-day-old pup was adopted by another female, BD, the research team continued their observations.
BD was not pregnant and did not have a pup of her own, but researchers found that she was lactating on the day Lilith died. After Lilith’s death, in addition to nursing, BD appeared to groom and share food with the pup more than any other female in the colony.
“Another intriguing discovery was that BD and another bat, called BSCS, both of which had been in captivity before, were the two bats who groomed the pup the most. Now we’re wondering if somehow the experience of being in captivity motivates individuals to invest in other bats at higher rates or adopt orphaned pups in critical need.”
Journal Reference: Razik, I., Brown, B.K.G., Page, R.A., Carter, G.G. Non-kin adoption in the common vampire bat. R. Soc. Open Sci., 2021 DOI: 10.1098/rsos.201927