PARENT SESSION

Merriam Awardee (Dr. Terry Bowyer)

SEXUAL SEGREGATION IN RUMINANTS: DEFINITIONS, HYPOTHESES, AND IMPLICATIONS FOR CONSERVATION. R. Terry Bowyer^1,2. ¹ Institute of Arctic Biology, University of Alaska Fairbanks, Faribanks, AK, USA; ² Present address: Department of Biological Sciences, Idaho State University, Pocatello, ID.

ABSTRACT- The concept of sexual segregation is an old one, first formally articulated by Charles Darwin. Among mammalian species, ruminants have been the focus of most research on this phenomenon. Sexual segregation has been defined traditionally as the differential use of space (and often habitat and forage) by the sexes outside the mating season, but other hypotheses related to activity patters of sexes recently have been forwarded. These new hypotheses cannot explain the spatial separation of sexes, or their differential use of habitats and forages. Sexual segregation should be considered in a niche framework wherein overlap on one niche axis is accompanied by avoidance on another. Moreover, sexual segregation is remarkably scale sensitive, which limits the usefulness of a comparative approach in investigating differences among species or populations. Requirements for demonstrating sexual segregation are stringent, and often not met. Many hypotheses for sexual segregation are too proximal to explain its widespread occurrence, are not independent, and sometimes are invoked in an a posteriori manner. Failure to discriminate between the potential evolutionary causes of sexual dimorphism in ungulates has lead to confusion over whether polygyny or intersexual competition has lead to sexual segregation. Neither exploitive nor interference competition between males and females is the cause of sexual segregation in ruminants. I suggest that only the gastrocentric hypothesis or predation risk may be necessary to explain sexual segregation, although additional research is necessary to verify some aspects of those hypotheses and to understand how they interact to produce the spatial arrangement of ruminants upon the landscape. The management and conservation of ungulates requires consideration that the sexes behave as if they were different species, which holds consequences for estimating populations, and manipulating harvest and habitats. This review resolves many long-standing problems related to sexual segregation, but much exciting research remains to be accomplished.

KEY WORDS: behavior, ruminants, adaptation, sexual segregation