Finding suitable wounds to suck blood from is a daily battle for vampire bats (Desmodus rotundus), but new research has found that these critters may swap information to boost their chances of finding a meal as it was discovered that they will meet up with pals while out on the prowl.
By combining observations with data from tiny, bat-sized tracking devices, researchers on a new study were able to prove that females will meet up with and remain in close proximity to bats they’re familiar with while foraging. They say the findings are evidence for the social bonds which exist among vampire bats, demonstrating that having some friends pays in more ways than one.
The study, published in the journal PLoS Biology, took 50 female common vampire bats (27 wild, 23 ex-captive) and sent them off into a cattle pasture in Tolé, Panama, with tiny trackers on their backs. The tracking data revealed that while most bats flew the roost on their own, closely bonded females would link up with their pals while out on the wing.
Bats who appeared popular in the roost were also associated with hanging around with more pals while foraging. And, in case you’re wondering how one goes about socializing while looking for blood, there’s a few ways the tracked bats were observed sharing in the experience.
“We have seen several different scenarios,” said study author Simon Ripperger in an email to IFLScience. “Three bats feeding from three different cows simultaneously while the cows were only 5 -10 meters apart from each other. We saw two bats feeding from the same cow but from different wounds. Vampire bats can even share and drink from the same wound.”
What’s more, the researchers took audio recordings of foraging bat calls in La Chorrera, Panama, and found three distinct call types including one new to science. They recorded a downward sweeping’ social call, an antagonistic ‘buzz’ call, and - the newbie - an n-shaped feeding call.
While the exact translations on these noises are up for debate, the researchers think they may have decoded the motivation behind such a social approach to searching for blood in groups. They posit that the bats may share information about the location of hosts and where on their body a puncture exists to make the search for an entry point all that much easier. Such a collaboration with trusted individuals will cut down on time and energy spent searching for nourishment and means they can share wound sites rather than having to dig out a new one.
“It is rather difficult for vampire bats to turn the blood they drink into fat storage,” said Ripperger. “Therefore, a vampire bat has to find food every couple of days. On the other hand, it is quite tricky to locate prey, open a wound and drink from it. It is, therefore, common that foraging bats return hungry to their dayroost.
“That's where the benefit of social or cooperative behavior kicks in. A hungry bat may receive a little bit of blood from a cooperative partner, which may save its life. For the donor, it's a real fitness cost but one that can be seen as an investment into the future. We know that the best predictor of receiving shared food is prior reciprocal donation. In other words, if a bat shares some of its meal with another bat, it may someday receive food from this particular individual when it itself is in need.”
Vampire bats have earnt something of a reputation as spooky, Halloween villains in wider society, but in reality these blood-sucking mammals are actually very charitable creatures. Living in roosts, they’ve been known to share blood with bats whose foraging was unsuccessful, effectively saving their life at a cost to their own. They’ve even been observed adopting the orphaned young of unrelated roost mates.
Not so spooky after all.