The importance of sex and spatial scale when evaluating sexual segregation by elk in Yellowstone

Gregory, Andrew; Lung, Mark; Gehring, Thomas; Swanson, Bradley

The forage-selection hypothesis (FSH) explains sexual segregation in ungulates as a function of differentdietary requirements producing different levels of habitat optimality, whereas the reproductive-strategyhypothesis (RSH) explains sexual segregation as a function of different survival strategies between the sexes.Based on observations of habitat use by elk (Cervus elaphus) in Yellowstone National Park, Wyoming withregard to varying levels of wolf encounter risk, we found that our determination of whether the RSH or FSHbest applied to sexual segregation varied by the scale at which we were measuring habitat use. At broad spatialscales we found no significant avoidance of wolves by elk. At the habitat scale we found that habitat use by elkwas consistent with predictions of the reproductive strategy in that female elk used habitats that offered abalance of forage and escape terrain for themselves and calves, and that the degree to which escape terrain waspresent was dependent upon the risk of wolf encounter. At the scale of the habitat patch we found thatdifferences in forage availability likely drove the differences in habitat use. Our results highlight the importanceof scale when investigating habitat use, nonlethal predation effects, and sexual segregation in ungulates.

The importance of sex and spatial scale when evaluating sexual segregation by elk in Yellowstone

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