Scratch my back, and I’ll scratch yours ― vampire bats have their own version of the saying. A new study published in the journal Proceedings of the Royal Society B indicates that the creatures feed others of their kind with blood so that the latter return the favour during times of need.
Vampire bats normally feed on the blood of other animals. They live in communities where they sometimes cooperate with each other for certain activities such as providing protection for their young, and, as has been discovered by scientists Gerald Carter and Gerald Wilkinson, they also help each other in cases of food shortage.
If a bat returns empty-handed from hunting, it can rely on others from its community for food. They share food (blood) via regurgitation – a method displayed by mother birds feeding their young. This is specially important for the bats because they might actually starve to death in a matter of two days owing to their high metabolism.
The researchers wanted to know whether they feed others out of altruism or because of mutual benefits? Is the shared feeding restricted to family members, or not?
By observing videos of a group of female bats (the sharing occurs mostly among them) including both relatives and non-relatives, it was found out that fasting bats obtained less blood when the researchers prevented donations from past donors, suggesting that donors are not interchangeable. It also seemed that bats having fed non-relatives would obtain more donations in times of need; they would help non-kin bats in order to increase their chance of having a donation when they would be longing for blood.
The researchers concluded that bats would share blood to ascertain that others would also share with them: a win-win situation.