Snuggle for survival

Photo by Gerald Carter

Along with skeletons and zombies, the fanged and hog-nosed visage of a bat is one of the most popular images for conjuring up fright at Halloween — and the vampire bat is the most celebrated of all bats known to the science of scaring.

There’s no reason to be frightened, though: There are no vampire bats in Ohio, or even in Count Dracula’s Transylvania. The only three species of vampire bat haunt only the tropical forests of Central and South America.

Since they rarely target humans, there’s not much chance that an Ohioan will ever encounter one — unless that Ohioan is Gerald Carter, assistant professor in the department of Evolution, Ecology, and Organismal Biology at Ohio State University. Carter studies bats, specifically vampire bats, and spent the past summer as he often does — capturing and studying vampire bats in the tropical forests of Central America.

His research has helped us understand that far from being monsters, vampire bats are good parents, forge strong “friendships” with other bats, and generally are models of cooperation, altruism, and social bonding. The two-ounce bats form long-term bonds and frequently help one another in ways that are costly to themselves, even with those who are not related. Understanding why cooperation can enhance survival and reproduction in the bat colony helps us appreciate why other mammals, including humans, benefit from what Carter calls “the snuggle for survival.”

“We often think humans are special because we are smart. But it’s our social smarts that really allow us to have the modern civilization that we do today,” Carter says. “If you took the smartest adult human and left them alone in a completely foreign environment, their best chance of survival is not to use their intelligence to fend for themselves, it would be to find a local tribe and then use their social intelligence to integrate into that society.”

Cooperation is essential to evolutionary success throughout nature. Social grooming is well-documented across species. Many animals regurgitate food for offspring, which helps to ensure the survival of the juveniles and continuation of the parents’ genes.

What makes vampire bats worthy of research is that they often will share their meal (which is, of course, another animal’s blood) with bats who are not related to them. This is no token gift — vampire bats are small (the common vampire bat weighs less than 2 ounces as an adult) and therefore can’t store a lot of energy. Missing meals for more than a day or two could end in starvation or reproductive failure. So wouldn’t evolution tell us that bats most willing to share would be most likely to die off?

The strategy seems to work, however, especially when the bat’s primary food-sharing partner is removed from the picture. Those bats with the most extensive network of food-sharing “friends” are the most likely to survive and their offspring to flourish.

“The question is then, what prevents cheating?” Carter asks. “Why not just take others’ help and not help anyone else?”

These are the questions Carter seeks to answer with his research, along with questions about how the social bonds form in the first place. One recent inquiry found that the development of social bonding is accelerated when two bat strangers are forced to live in close quarters (think college roommates, Carter says).

As previously noted, there are no vampire bats in Ohio. Ohio’s 13 bat species, all of which feast solely on insects, are not known to share food or groom one another, at least not in the way the subjects of Carter’s research do.

Still, there’s much to admire about Ohio’s bats. They huddle for warmth in their nursery colonies and they care diligently for their young. But Carter doesn’t feel the need to defend bats. Despite the persistent and erroneous treatment of bats at Halloween, hostility toward bats is fading, he says.

“Kids really love bats,” he says. “It seems to me sometimes that they are almost like the new dinosaurs. If you go to a library and look in the animal section of the kids area, you’ll see multiple books about bats and why we should care for them.”