Shy female kangaroos seek safety in numbers and have fewer preferred friendships

Personality and behavioral syndromes are of significant interest to a wide range of biological disciplines. Recent research using network analysis techniques has revealed widespread variation among individuals in sociability, which is a major axis of personality that creates the social microenvironment in which individuals express all other behaviors. We investigated the relationship between sociability and boldness, another fundamental personality axis, using a wild population of eastern grey kangaroos (Macropus giganteus) tested in their natural environment. We studied 2 dimensions of sociability (grouping behavior and association patterns). Over 2 years we found significant within-individual consistency and interindividual variation in the foraging group sizes of 171 females. Network analysis comparisons of 103 females between the years, using HWIG (an association index that controls for gregariousness), showed that individuals were also highly consistent in their social network measures. We tested the boldness of 51 of these females 6–21 times each over 18 months, using flight initiation distance tests; individuals were also highly consistent in this measure of personality. Shy females had significantly larger mean foraging group sizes. After controlling for gregariousness and space use, shy females had fewer preferred associates than bolder females. Therefore, boldness can have an important influence on the size and composition of foraging groups and thus social networks, in wild mammals.