Vampire bats regurgitate bloody dinners for their hungry girlfriends

Vampire Bats develop and maintain social bonds similar to friendships - sharing blood meals.

Vampire Bats develop and maintain social bonds similar to friendships – sharing blood meals. (Sherri and Brock Fenton /)

Nothing cries spooky season as much as vampire bats. Leathery wings, snarling snouts and, of course, the exclusive blood diet, make these unique mammals real-life monsters. However, in reality, these seemingly terrifying creatures are actually very friendly, at least between them.

A study published on Halloween in cellular biology found that vampire bats develop and maintain social bonds similar to friendships. Biologists knew that these creatures were particularly hospitable to each other because of their rare grooming and sharing habits. But until now, scientists had been unable to prove that they had forged long-standing relationships.

Researchers Gerald Carter, associate professor at Ohio State University, and Simon Ripperger, a postdoctoral fellow at the Smithsonian Institute, hypothesized that the links between bats developed during their captivity would be maintained after their return. in the environment. For this study, the researchers mixed two groups of bats: one cohort was born in captivity and another (200 people) was born of a wild colony.

To build relationships, the scientists fasted each bat one at a time. When a bat is hungry for blood for one night, his peers regurgitate last night's dinner as a "gift of food" and comfort each other. According to Carter, women are the only ones to have this behavior. (It seems to Carter that men are too preoccupied with fighting over established territories to form friendships.)

After 22 months in captivity, the bats were released at home – a hollow tree in a pasture of Panamanian cow that smells like bat poo. To follow the social interactions of bats, the team glued tiny sensors developed by Ripperger and his colleagues, electrical engineers and computer scientists, behind the bats. Lighter than a penny and the size of a finger, these automated sensors are unique in their ability to track social networks of small groups of animals by measuring their proximity to each other. Unlike other nearby technologies, they are able to capture evolving networks of relationships, even in difficult access sites such as small caves or, in this case, hollow, stinking trees.

These sensors found captive bats captive in spite of being able to roam anywhere or associate with any of their other 200 roommates.

"Our results show that this high-resolution tracking method can reveal relationships that have ecological consequences," says Carter. Previous scientific evaluations of "friendship" in animals come almost exclusively from primate research. "We can now see that some relationships with animals are independent of the place."

However, not all friendships have stood the test of time. After only six days, bats born in captivity took flight after failing to assimilate to the colony. Even those born from wild bats have been ousted. It is important to note that the study's observations are only eight days old, with the sensor measuring the proximity of bats falling from the back of one of the subjects. As a result, researchers can not know for sure how long these "friendships" lasted for a week.

"It's a nice illustration that shows how the social structures of animals depend on both their internal preferences of each other, but also their external environment, because not all links last," says Carter, who has been studying vampire bats for a decade. "Even in a completely different setting, these bats were always drawn to each other."

If you follow, maintaining about twenty mini-monsters sucking blood requires a lot of blood. Twice a month, Carter and Ripperger went to a local abattoir to fill a five-gallon bucket filled with burgundy blood. They then quickly returned the car to the laboratory (the blood quickly deteriorated) where they froze the blood in bottles. Only once did they spill the entire contents of the bucket into Carter's back seat. At the time of feeding, the frozen blood was dispensed into plastic tubes forming small reservoirs of liquid.

"The tanks are usually used to give birds water, but we only use blood," says Carter. He and Ripperger are laughing. "Once, an assistant fainted when she saw this."

No matter how vampire bats feast on blood, one thing seems true: those who share their morbid meal are on the road to friendship.