In 2016 and 2017, we captured female vampire bats and then released them back into the wild almost two years later to track their wild association networks. During their time in captivity, 12 of the females gave birth to pups. Would these captive-born bats be able to survive in the wild?
Jineth Berrío-Martínez conducted an experiment on whether the captive-born bats could feed on a live chicken (alone or with the presence of their mother).
First, we decided to buy a bunch of chickens to use as hosts. My wife Michelle, who is a farmer, helped us build a chicken coop that was secure against predators.
Each day, Jineth would isolate a chicken and a vampire bat and film the feeding. Some of the results were unclear and unexpected. For example the mothers never fed on the chickens (see the paper for more information), but we did answer the main question: yes captive born bats can feed on a live animal.
Jineth tried a number of different setups in a series of pilot trials before finding one that worked well. The vampire bat had to be able to access the chicken but also get away from it. The example below shows a cage that a vampire bat could enter and exit but not the chicken. We used a different setup in the actual tests (see the videos below) where the bat could hide in roost box.
Here is a video showing a captive-born bat feeding on a live animal for the first time.
We had previously found that younger bats are far more exploratory and more likely to crawl and jump on top of novel objects, and we observed that this was equally true when feeding on novel live animals! Overall, it seemed that the young vampire bats could feed on a live animal, but they were not particularly good at it when compared to some wild-caught vampire bats. We could not compare them with their mothers however, because none of the mothers even tried to feed on the chicken. Instead, they hid in their roost box the whole night.
Sam Kaiser also did an experiment testing whether captive-born or wild-born bats prefer cold blood (which is what we give them in captivity) or warm blood (which is what they would feed on in the wild). It turns out that the vampire bats don’t really care much at all about the blood temperature when the blood is in a feeder spout. This might seem a bit surprising because vampire bats use heat to find blood near the skin, but it’s not too surprising to consider that vampire bats use many different cues (echolocation, olfaction, vision, etc) and they probably learn to use different cues in different contexts.
Study: Berrío-Martínez J, Kaiser S, Nowak M, Page RA, Carter GG. 2019. The role of past experience in development of feeding behavior in common vampire bats. PeerJ 7:e7448https://doi.org/10.7717/peerj.7448