Can intrinsic foraging efficiency explain dominance status? A test with functional response experiments.

The functional response describes how food abundance affects the intake rate of foraging individuals, and as such, it can influence a wide range of ecological processes. In social species, dominance status can affect the functional response of competing individuals, but studies conducted in an interference-free context have provided contrasting results on the extent of between-individual variability in functional response. We tested the prediction that individuals intrinsically differ in their functional response, and that these differences could predict body weight and dominance status in social species. We used goats as a model species and performed foraging experiments to assess the functional response of these goats in an interference-free context. Our results show that some individuals are consistently better foragers than others, and these individuals were more likely to be heavier and dominant. Parameters of the functional response are, however, more strongly associated with dominance status than with body weight. We conclude that interference while foraging is not needed to explain body weight differences between dominant and subordinate individuals. We suggest that these differences can emerge from intrinsic differences in foraging efficiency between individuals, which could also allow better foragers to demonstrate greater tenacity during agonistic interactions.