Vampire bat
Ecology and life cycle

Vampire bats tend to live in colonies in almost completely dark places, such as caves, old wells, hollow trees, and buildings. They range in Central to South America and live in arid to humid, tropical and subtropical areas. Vampire bat colony numbers can range from single digits to hundreds in roosting sites. The basic social structure of roosting bats is made of female groups and their offspring, a few adult males, known as "resident males", and a separate group of males, known as "nonresident males". In hairy-legged vampire bats, the hierarchical segregation of nonresident males appears less strict than in common vampire bats. Nonresident males are accepted into the harems when the ambient temperature lowers. This behavior suggests social thermoregulation.

Resident males mate with the females in their harems, and it is less common for outside males to copulate with the females. Female offspring often remain in their natal groups. Several matrilines can be found in a group, as unrelated females regularly join groups. Male offspring tend to live in their natal groups until they are about two years old, sometimes being forcibly expelled by the resident adult males. Vampire bats on average live about nine years when they are in their natural environment in the wild.

Vampire bats form strong bonds with other members of the colony. A related unique adaptation of vampire bats is the sharing of food. A vampire bat can only survive about two days without feeding, yet they cannot be guaranteed of finding food every night. This poses a problem, so when a bat fails to find food, it will often "beg" another bat for food. A "donor" bat may regurgitate a small amount of blood to sustain the other member of the colony. For equally familiar bats, the predictive capacity of reciprocity surpasses that of relatedness. This finding suggests that vampire bats are capable of preferentially aiding their relatives, but that they may benefit more from forming reciprocal, cooperative relationships with relatives and non-relatives alike. Furthermore, donor bats were more likely to approach starving bats and initiate the food sharing. When individuals of a population are lost, bats with a larger number of mutual donors tend to offset their own energetic costs at a higher rate than bats that fed less of the colony before the removal. Individuals that spend their own energy as a social investment of sorts are more likely to thrive, and higher rates of survival incentivize the behavior and reinforce the importance of large social networks in colonies. These findings contradict the harassment hypothesis—which claims that individuals share food in order to limit harassment by begging individuals. All considered, vampire bat research should be interpreted cautiously as much of the evidence is correlational and still requires further testing.

Another ability that some vampire bats possess is identifying and monitoring the positions of conspecifics (individuals of the same species) simply by antiphonal calling. Similar in nature to the sound mother bats make to call to their pups, these calls tend to vary on a bat to bat basis which may help other bats identify individuals both in and outside of their roost.

Vampire bats also engage in social grooming. It usually occurs between females and their offspring, but it is also significant between adult females. Social grooming is mostly associated with food sharing.
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