Other animals also accept certain kinds of social agreements with one another. For example, some bat species share food they find with other members of their community who are not related to them. A bat cannot be forced to share food against its will, because the process involves regurgitating food into the recipient’s mouth. Each bat remembers which individuals in the community helped it when it was hungry and which refused to help when it needed support, and responds to them accordingly.
It is not unusual for bats to go several days without finding food. In such cases, their survival depends on having friends. In effect, by sharing food with others, these bats buy an insurance policy. A bat with a large network of friends is much more likely to survive, while a bat that does not honour these agreements—by failing to help those who helped it—will soon have no friends when it needs support.