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Résumé |
Resource sharing outside the kinship bonds is rare. Besides humans, it occurs in
chimpanzees, wild dogs and hyenas as well as in vampire bats. Resource sharing is
an instance of animal cooperation, where an animal gives away part of the
resources that it owns for the benefit of a recipient. Taking inspiration from
blood-sharing in vampire bats, here we show the emergence of generosity in a
Markov game, which couples the resource sharing between two players with the
gathering task of that resource. At variance with the classical evolutionary
models for cooperation, the optimal strategies of this game can be potentially
learned by animals during their life-time. The players act greedily, that is, they
try to individually maximize only their personal income. Nonetheless, the
analytical solution of the model shows that three non trivial optimal behaviors
emerge depending on conditions. Besides the obvious case when players are selfish
in their choice of resource division, there are conditions under which both
players are generous. Moreover, we also found a range of situations in which one
selfish player exploits another generous individual, for the satisfaction of both
players. Our results show that resource sharing is favored by three factors: a
long time horizon over which the players try to optimize their own game, the
similarity among players in their ability of performing the resource-gathering
task, as well as by the availability of resources in the environment. These
concurrent requirements lead to identifying necessary conditions for the emergence
of generosity. |
