A Model of Social Organization and the Evolution of Food Sharing in Vampire Bats.

This article is aimed at exploring the role of groups in the evolution of a well-known form of altruism: blood sharing among vampire bats. In particular, we are interested in the formation and maintenance of new social structures (roosts) from initial populations as a consequence of both demographic growth and social organization. The example of vampire bats is especially interesting because of the flexible roost-switching behavior shown by these animals in nature. The main hypothesis made in this article concerns the role of grooming networks in roost formation, and was investigated by means of simula tion grounded on ethological evidence. The use of simulation allows the discussion of generative hypotheses on the origin of roosts, which are emergent from individual behavior. Besides confirming the main expectations, the results point to the need for a natural ordering in grooming partner selection. This ordering can be obtained not only through kin-based groups but also through the maintenance of a non kin-based precedence rule.