Kangaroos’ boldness relates to their social patterns and assortment (#134)
Consistent individual differences in behaviour (called personality or temperament) have been described in a wide range of taxa in both wild and captive populations, and are increasingly considered to be of ecological and evolutionary significance. Boldness/shyness, or risk-taking/risk-aversion, is a dimension of animal personality that has been investigated in a large number of empirical studies of different species. However, the relationship between boldness and sociability, a less-studied axis of personality, does not show consistent patterns among species, perhaps at least partly because sociability can be measured in many different ways. There has also been little research on whether relationships between these two personality axes remain stable over long time periods or across varying environments. Our four year study of a wild population of over 200 individually identified eastern grey kangaroos (Macropus giganteus) has provided a model system in which to explore how individuals’ boldness relates to various metrics of their sociability, and how consistent these relationships are across time and changing environmental conditions. We have previously reported that individual females differ significantly in their degree of boldness, and that bolder individuals exhibit different patterns of sociability than shyer animals. Here we show that individuals were highly consistent in boldness, and in the number of preferred companions that they chose to associate with, over a four-year period. The relationships between boldness and sociability, shown by shyer individuals preferring to forage in larger groups and having fewer preferred companions, also remained consistent over this time despite changes in the physical and social environments of the population. Finally we show that social assortment of adult female kangaroos occurred based on similarity in boldness. These findings show that individuals’ boldness levels are tightly linked to their social patterns.