Reciprocal Altruism Between Male Vampire Bats, Desmodus Rotundus

Reciprocal altruism is an example of social behaviour that has generated much interest among evolutionary theorists, but relatively few well-documented case studies. Among mammals, reciprocal altruism has been reported for the dwarf mongoose, Helogale parvula (Rood 1983), naked mole rats, Heterocephalus glaber (Jarvis 1978), impala, Aepyceros melampus (Hart & Hart 1992) and a few other species, but the best known and most intensively studied example is the regurgitation of blood-meals by successfully foraging adult vampire bats to unsuccessful individuals. This behaviour has apparently evolved in response to the finely balanced energy budget of vampires, which can result in starvation following as little as 48-72 h of food deprivation (McNab 1973). A foraging situation that results in an average of ~8% of adults failing to feed successfully on any given night (Wilkinson 1984), combined with the low fecundity of vampire bats, makes food sharing an essential element of survival