The ability of social animals to recognise and differentiate between members of their group is of fundamental importance, but has so far primarily been studied in mammals. A new research study has revealed that ravens (Corvus corax) are able not only to distinguish whether other individuals are familiar to them, but also the valence of their relationship - whether previous experiences with said individual have been positive or negative, defining them as either ‘friend’ or ‘foe’ - which may have been established as long as three years ago. In their early years, ravens live in dynamic nonbreeder flocks and engage in complex social interactions, such as sharing the location of food or, opposingly, deceiving others in order to have sole access to a particular food cache. Over time, ravens therefore establish relationships with others who are either deemed affiliates (friends) or nonaffiliates (foe). A relationship with an affiliate is a valuable survival asset, making the ability to discriminate members of the group a great advantage. Scientists have now discovered that this is indeed the case. The familiarity of another individual to a raven is reflected in the number of responding calls, where more familiar birds will elicit increased call frequency. Contrastingly, relationship valence is reflected in call modulation - the properties of the call in terms of sound. Individuals that the raven is familiar with but that were nonaffiliates elicited a lower and rougher call than those that were affiliates. The findings confirm that ravens have a long-term memory of familiar group members and are able to differentiate between those that have acted as friends or foes in the past. Studies of other species of bird of varying degrees of sociality will help to reveal more about avian cognition and social interactions.
Ref: Boeckle M. & Bugnyar T. (2012) Long term memory for affiliates in ravens. Current Biology Published Online [link]