ABS 2022
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Are Aspects of Horn Morphology Associated with Male Bighorn Sheep Reproductive Success and Female Mate-Choice?
Tanisha C Henry, Kathreen E Ruckstuhl. University of Calgary, Calgary, Alberta, Canada

Sexual selection often leads to exaggerated secondary selected traits, such as large horns in bighorn rams (Ovis canadensis), which confer the bearer fitness benefits. These traits are the product of female mate choice and male-male competition for limited mating opportunities. Elaborate traits are expensive to develop and maintain, and thus an honest signal indicating the quality of an individual to potential mates. Bighorn rams establish a dominance hierarchy before the mating season, and monopolize breeding with one female at a time, leading to a high skew in reproductive success of dominant males. It is unclear to what degree females can exert mate choice when they are tended by a dominant male, but they could make themselves available to other males, indicating a limited degree of female mate choice. Morphological traits such as horn length and body mass, in addition to age and social experience, are predictors of reproductive success. I am investigating which aspects of a ram’s horn shape (volume, circumference at the base, coil ratio) might be associated with his dominance rank and attractiveness to females.