Social attention across development in common ravens and carrion/hooded crows

Abstract

Social attention involves individuals attending to the presence, identity and/or behaviour of others, which may facilitate cooperation, communication and social learning. Individuals may be selective in when and to which individuals they attend, which may be influenced by social context (e.g. observer identity) and development. In 10 carrion/hooded crows, Corvus corone corone/C. c. cornix, and nine common ravens, Corvus corax, we tested the influence of social context (alone, sibling/affiliate, nonsibling/nonaffiliate, heterospecific) on behavioural responses (item manipulation, caching and ‘head and body out of sight’, i.e. barrier use) with familiar food and objects. We tested subjects during development at fledging (1–2 months), juvenile (3–8 months) and subadult (14–18 months old) stages. Subjects were hand reared and housed in comparable conditions. These two species are closely related, generalist corvids, which will routinely cache (i.e. hide food and other items for later recovery) and engage in cache-pilfering (stealing) strategies. Item manipulation and caching may contribute to the development of physical and/or social skills. Subject behaviour was influenced by social context, with birds showing higher frequency of ‘head and body out of sight’ (barrier use) behaviour with (any) observer present than when alone. Observer identity had no effect, suggesting item interaction may have facilitated development of physical (rather than influencing social) skills in this setting. There were developmental effects, including increased manipulation and use of barriers as juveniles, and increased caching with age. Ravens cached more than crows. Objects were manipulated more frequently than food. Barriers were used more with food, indicating food was more actively hidden, while object manipulation may promote low-risk interaction and learning. We discuss our findings in relation to social and developmental influences on behaviour, in relation to social attention across ontogeny in animals.