title: Tolerance and reward equity predict cooperation in ravens (Corvus corax).
abstract: Cooperative decision rules have so far been shown experimentally mainly in mammal species that have variable and complex social networks. However, these traits should not necessarily be restricted to mammals. Therefore, we tested cooperative problem solving in ravens. We showed that, without training, nine ravens spontaneously cooperated in a loose-string task. Corroborating findings in several species, ravens' cooperative success increased with increasing inter-individual tolerance levels. Importantly, we found this in both a forced dyadic setting, and in a group setting where individuals had an open choice to cooperate with whomever. The ravens, moreover, also paid attention to the resulting reward distribution and ceased cooperation when being cheated upon. Nevertheless, the ravens did not seem to pay attention to the behavior of their partners while cooperating, and future research should reveal whether this is task specific or a general pattern. Given their natural propensity to cooperate and the results we present here, we consider ravens as an interesting model species to study the evolution of, and the mechanisms underlying cooperation.
authors.affiliation: University of Vienna, Department of Cognitive Biology, Vienna, Austria.
authors.forename: Jorg J M
authors.initials: JJ
authors.lastname: Massen
authors.affiliation: University of Vienna, Department of Cognitive Biology, Vienna, Austria.
authors.forename: Caroline
authors.initials: C
authors.lastname: Ritter
authors.affiliation: University of Vienna, Department of Cognitive Biology, Vienna, Austria.|Haidlhof Research Station, University of Vienna and University of Veterinary Medicine, Bad Vöslau, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bugnyar
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D003299:Cooperative Behavior; D046368:Crows; D005260:Female; D007398:Interpersonal Relations; D008297:Male; D011340:Problem Solving; D012201:Reward