Abstract

Measuring rates of self-scratching provides a powerful index of anxiety in non-human
primates, and investigating the relationship between self-scratching and dominance rank can
shed light on the ‘emotional costs’ of holding different positions in the hierarchy. Here we
explored the relationship between self-scratching rates and rank in wild adult female Barbary
macaques (Macaca sylvanus) in Morocco.We found a significant correlation between rank and
females’ mean self-scratching rates over the study period, with subordinates showing higher
rates of self-scratching. Analysis of temporal variation in females’ self-scratching rates
indicated that while these rates were related to measures of both grooming and aggression, the
relationship between rank and self-scratching remained significant even after controlling for
these effects. Our data suggest that lower ranked female Barbary macaques suffer higher levels
of anxiety than more dominant individuals, and hence that there is an emotional cost associated
with having low social status in this species.