An ‘unkindness’ of ravens? Measuring prosocial preferences in Corvus corax

In recent years there has been considerable research effort to determine whether other species exhibit prosocial motivations parallel to those of humans; however these studies have focused primarily on primates, and with mixed results. We presented captive ravens with a modified prosocial choice task which aimed to address several criticisms of previous methods by including a stringent pre-training regime and a setup that disentangles motivation to provision a conspecific from motivation to feed next to one. In this task subjects (N=6) received no rewards for themselves but could choose to deliver food rewards to either a conspecific or an empty, inaccessible compartment. Subjects did not demonstrate any prosocial tendencies (i.e., they did not preferentially choose to reward a conspecific over the empty compartment), and instead often ceased pulling on test trials when they received nothing for themselves (up to 70% of 80 trials with a partner present, up to 83% of 40 trials in a non-social control condition). The relationship between the subject and the partner had no influence on the subject’s choices; however subjects were more likely to pull immediately after performing socio-agonistic displays. Our results contribute to a growing body of evidence that despite their sophisticated social cognitive abilities and range of cooperative behaviours exhibited in the wild, un-paired (or unbonded) ravens do not seem to act to benefit conspecifics in the absence of immediate self-gain.