Social factors during foraging bouts influence sexual segregation in Roosevelt elk
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Spatial patterns of large ungulates occurring at broad scales can often be explained by fine-scale processes that function at the level of an individual animal. To better understand broad-scale sexual segregation, we examined fine-scale processes in a non-migratory population of Roosevelt elk (Cervus elaphus roosevelti) in the Redwood National and State Parks, California, USA that exhibited a change in sexual segregation over time. We assessed the potential influence of two fine-scale mechanisms: the availability of forage abundance and social factors during the forage bout. Per capita forage availability was estimated for comparison between two meadow complexes (2005- 2016) to determine if selectivity for one meadow complex by males (and thus sexual segregation) could be explained by the constraints of their greater absolute metabolic requirements. To assess the influence of social factors (such as group size, group type, or proximity of conspecifics) during the foraging bouts, focal observations were collected from adult male and female elk from 2009 to 2016. These data were used to conduct AIC model selection analyses to determine the best fit, mixed-effect models for predicting the distance traveled, the variance in turning angles, and the proportion of time the animal spends with its head out of the feeding position during a foraging bout. Interestingly, we found that the availability of forage biomass was likely not the driver for males and females using separate meadow complexes. This study instead found that behavioral differences existing between males and females, as well as between males in single-sex groups and males in mixed-sex groups may have affected sexual segregation. As group size increased, males in male-only groups tended to move farther and in more direct paths than females in order to avoid other animals. In addition, males in both female and male- only groups were more vigilant than females when foraging in close proximity to conspecifics, yet the time allotted to vigilance increased at a greater rate for males in male-only groups. These asynchronous responses to social factors in male-only versus female groups may explain the exclusive, male-only use of a meadow complex from which females were recently extirpated. We can therefore conclude that sexual segregation, in this population of Roosevelt elk is driven in part by fine-scale foraging behaviors.