About Mule Deer

SEXUAL SEGREGATION IN MULE DEER

R. Terry Bowyer
Department of Biological Sciences
Idaho State University

The sexes of mule deer live apart for much of the year, a pattern typical of sexually dimorphic (males larger than females) and polygynous (males mate with more than one female) ruminants (mammals that chew their cuds). Sexes of deer occur on the same areas for rut (mating) and may congregate on limited winter ranges or briefly associate during spring green up. Nonetheless, by fawning season, bucks and does use spatially different areas. Body-size and rumen differences result in bucks being able to digest a lower-quality diet than does, but they require absolutely more forage than do females. The digestive system of does is modified each spring to allow them to digest high-quality food to help support the high costs of lactation. Does with fawns at heel also are more vulnerable to predators, which effects their use of some habitats. Consequently, the sexes require different habitats, which mean that habitat manipulation to benefit deer may benefit one sex, potentially to the detriment of the other. These outcomes have resulted in some biologists believing that the sexes of deer should be managed as if they were separate species.

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