Oral Presentations
The Breaking Point: Examining Antler Breakage Patterns and Morphological Variation in Rocky Mountain Elk (Cervus canadensis)
Presentation Type
Presentation
Faculty Mentor’s Full Name
Douglas Emlen
Faculty Mentor’s Department
Biological Sciences
Abstract / Artist's Statement
Sexually-selected weapons, like antlers, can be used as tools in combat or visual signals of social rank and fighting ability. Specifically, Cervus canadensis, or the North American elk, utilizes antlers in early, non-contact assessment behaviors (i.e., bulging, parallel walking, posturing) before yielding antlers in dangerous battles of twisting and pushing. Bulls assess each other during early stages of contests and by result, full blown fights are very rare. Based on animal contest theory, dominant males should have the most to gain from mating and should be the only ones engaging in escalated fights, but fighting frequency amongst age classes has not been explicitly described in elk. This study measured the morphological variation by comparing the symmetry and breakage patterns from harvested males at the Darby, MT FWP station. Specifically, we measured the difference between areas of the antlers we determined function exclusively as tools and signals. We explored specific features of morphology such as antler length, antler curl, span, tine placement, and asymmetry as potential factors contributing to breakage. In our study, we observed extremely high rates of antler damage (30% of 82 males) in predominantly younger males (less than 6 tines), and we found younger males broke tines near the base of the skull (inferior). When we compared symmetry of the tools and signals features, we found tools features are less variable, and signal asymmetry increased with antler length. While our symmetry results support our hypothesis that signal traits would be more variable and structurally weaker than tools, our breakage patterns were unexpected based on contest theory predictions. Our future directions include performing biomechanical models on antler durability in battle and testing extrinsic factors, such as harvest or disease, on male fighting behaviors and breakage patterns.
Category
Life Sciences
The Breaking Point: Examining Antler Breakage Patterns and Morphological Variation in Rocky Mountain Elk (Cervus canadensis)
UC 331
Sexually-selected weapons, like antlers, can be used as tools in combat or visual signals of social rank and fighting ability. Specifically, Cervus canadensis, or the North American elk, utilizes antlers in early, non-contact assessment behaviors (i.e., bulging, parallel walking, posturing) before yielding antlers in dangerous battles of twisting and pushing. Bulls assess each other during early stages of contests and by result, full blown fights are very rare. Based on animal contest theory, dominant males should have the most to gain from mating and should be the only ones engaging in escalated fights, but fighting frequency amongst age classes has not been explicitly described in elk. This study measured the morphological variation by comparing the symmetry and breakage patterns from harvested males at the Darby, MT FWP station. Specifically, we measured the difference between areas of the antlers we determined function exclusively as tools and signals. We explored specific features of morphology such as antler length, antler curl, span, tine placement, and asymmetry as potential factors contributing to breakage. In our study, we observed extremely high rates of antler damage (30% of 82 males) in predominantly younger males (less than 6 tines), and we found younger males broke tines near the base of the skull (inferior). When we compared symmetry of the tools and signals features, we found tools features are less variable, and signal asymmetry increased with antler length. While our symmetry results support our hypothesis that signal traits would be more variable and structurally weaker than tools, our breakage patterns were unexpected based on contest theory predictions. Our future directions include performing biomechanical models on antler durability in battle and testing extrinsic factors, such as harvest or disease, on male fighting behaviors and breakage patterns.