A female vampire bat has adopted an orphaned baby bat and begun nursing it, after creating a close social bond with the babyâs mother before she died.
Although female bats live in âmaternity coloniesâ, sometimes composed of hundreds of bats, they seem to raise their young individually rather than as a community. This rare observation of a bat adopting an unrelated infant gives further insight into the complexity of social relationships between individual bats, says Imran Razik at The Ohio State University.
âThe cool thing about vampire bats is they form these long-term social relationships with one another, which are in some ways comparable to human friendships,â says Razik. âWith this adoption, something we donât usually see, weâve had the chance to contextualise this event very easily by having a recorded, long-term history of the social interactions [leading up to the adoption].â
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Razik and his colleagues at the Smithsonian Tropical Research Institute in Panama were studying the social behaviour of common vampire bats (Desmodus rotundus) at the time of the adoption. They captured 23 adult female bats from three wild colonies located hundreds of kilometres from each other, then put them together in a single captive colony to see how they developed relationships with strangers. Female vampire bats can form social bonds with other bats, grooming each other and sharing food by licking each otherâs mouths.
One bat fell ill during the study and died within weeks of giving birth. To the researchersâ surprise â and relief â another bat adopted the infant, says Razik.
By viewing hundreds of hours of video recordings of their social interactions, the researchers could fully trace the development of the relationship between the sick mother bat (âLilithâ) and the adoptive bat (âBDâ), who wasnât pregnant or nursing. They had initially shown a lot of mutual grooming, suggesting they were bonding, says Razik.
The healthy bat shared food much more often than Lilith did, a trend that increased as Lilith became sicker with what the researchers believe was gastrointestinal illness.
BD also helped take care of Lilithâs baby, grooming it and even nursing it, although she herself didnât have a baby.
When Lilith died 19 days after giving birth, BD fully adopted the baby and raised it as her own. âI manually expressed milk from BDâs nipple, and I thought, âwow, sheâs actually nursing this pupâ, and I knew this was a really great story,â says Razik.
The other 21 females in the colony didnât help Lilith or her pup to nearly the same extent.
âWe set out to study partner choice, and why bats invest in one other and how they form these relationships,â says Razik. âThis adoption has really been an interesting contribution to that.â
Royal Society Open Science
