Vampire Bats Make Friends By Sharing Blood

Vampire bats share food with non-kin in order to widen their social networks. SuperStock/Alamy
Ben Taub 18 Nov 2015, 15:31

They may be blood-thirsty creatures of the night, but vampire bats are also surprisingly altruistic and sociable, as new research into their food-sharing habits suggests. The study, which appeared today in Proceedings of the Royal Society B, sheds new light on the generosity of these flying mammals, indicating how sharing their crimson sustenance helps to foster key social relationships.

The fact that vampire bats regurgitate blood in order to feed those who have been unsuccessful in their nightly hunt is not new information. However, until now, researchers had struggled to understand why some females share their food with bats who are not part of their own kin group.

In order to solve this puzzle, a team of biologists at the Smithsonian Tropical Research Institute in Panama conducted a series of experiments that enabled them to observe the bats’ sharing patterns more closely. This involved starving certain bats for periods of 24 hours, before reintroducing them into their social groups and noting which members did and didn’t offer them food.

As it turns out, bats tend to share with others who have previously shared with them in their times of need, and will often shun those who have displayed stinginess in the past – regardless of whether or not these bats are part of their own kin group. Interpreting these results, the study authors conclude that this practice plays a vital role in the creation of social networks, which ultimately benefit the individual as well as the group.

“Non-kin sharing widens social network size not merely by increasing groupmate survival, but by creating or strengthening social ties that yield reciprocal returns,” the study claims. “As a consequence, individuals that feed more non-kin should have more donors when the need arises.”

Nurturing these social relationships is vitally important to vampire bats, since they can easily starve if they go more than a couple of days without securing a meal of their own. As a result, the bats in the study displayed a propensity to strengthen as many of these non-kin bonds as possible, thereby increasing their number of potential donors.

This information will no doubt cause many to view vampire bats in a different light, as it shows a nicer, more vulnerable side. Of course, others will insist on shattering this image by pointing out that the creatures are equipped with infrared sensors that enable them to home in on their prey’s veins, and that their thirst for blood has caused them to lose the ability to taste other things.

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