Crows restrict the majority of their social interactions to close family members unless there is important information on food resources that could be shared, finds a study in Nature Communications. The authors suggest that changes in the dynamics of their social networks could facilitate the spread of cultural traits such as tool-use.
New Caledonian crows are known to utilise tools, like small twigs and branches, to probe holes in tree bark for their insect prey. These skills are thought to be passed to other observing crows through social learning, although the extent to which this knowledge may be transmitted is likely to depend on the structure of social interactions within a group.
James St Clair and colleagues use high-resolution wireless technology to track interactions between crows in multi-family groups, finding that the majority of interactions occur between only a small number of genetically-related individuals or mate-pairs. However, when a food source that requires tools to exploit is introduced, overall connectivity of the network increases quickly, as do interactions between individuals who had not previously associated with one another.
No such changes were observed when the same food source was introduced halfway between the territories of two different multi-family groups, suggesting these interactions are highly localised. This expansion of local social network connectivity in response to food suggests that opportunities for the transmission of cultural information also increase, potentially driving the spread of tool-use.