Third-party interventions of common ravens, Corvus corax

Abstract

The social intelligence hypothesis suggests that cognitive capacities evolved because of selection pressures related to increasing social complexity. For instance, social animals may need to monitor the relationships of others and intervene in them if that is ultimately beneficial to themselves. Traditionally, such third-party interactions are studied by examining coalitionary support during conflicts. However, growing evidence shows that some animals also intervene in others’ positive social interactions. To aid our understanding of the patterns of such interventions in the wild, we examined third-party interventions in both positive and negative interactions in a population of individually marked wild ravens. Although we found that interventions in negative interactions were more frequently observed than those in positive interactions in this wild population, both were relatively common and, in fact, occurred in almost exact proportions relative to the number of such interactions (∼10% of ad libitum interactions in both cases). Interventions were mostly active (compared to mere approaches) and aggressive. However, the mode of intervention varied across interactions. In positive interactions, interventions were mostly impartial, whereas in negative interactions, interventions were not, targeting one of the two partners. Neutral or policing interventions in negative interactions were rare. More than half of negative interventions reflected coalitionary support for the aggressor and a quarter for the victim. Furthermore, the likelihood of initiating an intervention and being the target of an intervention varied according to age, sex, rank, residency status and affiliation index. Taken together, our results provide a complete overview of third-party interventions in wild ravens and suggest that ravens use these interventions selectively and potentially even strategically. Future comparative studies may allow investigations into whether the necessity of such social strategies may have been a selection pressure regarding intelligence in animals.