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Disease and secondary sexual traits: effects of pneumonia on horn size of bighorn sheep |
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| Authors: | Alynn M. Martin John T. Hogg Kezia R. Manlove Tayler N. LaSharr Justin M. Shannon Doug E. McWhirter Hollie Miyasaki Kevin L. Monteith Paul C. Cross |
| Affiliation: | 1. U.S. Geological Survey, Northern Rocky Mountain Science Center, 2327 University Way, Suite #2, Bozeman, MT, 59715 USA;2. Montana Conservation Science Institute, Missoula, MT, 59803 USA;3. Department of Wildland Resources and Ecology Center, Utah State University, Logan, UT, 84322 USA;4. Haub School of Environment and Natural Resources, Wyoming Cooperative Fish and Wildlife Research Unit, Department of Zoology and Physiology, University of Wyoming, Laramie, WY, 82071 USA;5. Utah Division of Wildlife Resources, Utah Department of Natural Resources, Salt Lake City, UT, 84116 USA;6. Wyoming Game and Fish Department, Cheyenne, WY, 82006 USA;7. Idaho Department Fish and Game, Boise, ID, 83712 USA |
| Abstract: | Secondary sexual traits (e.g., horns and antlers) have ecological and evolutionary importance and are of management interest for game species. Yet, how these traits respond to emerging threats like infectious disease remains underexplored. Infectious pneumonia threatens bighorn sheep (Ovis canadensis) populations across North America and we hypothesized it may also reduce horn growth in male sheep. We assess the effect of pneumonia on horn size in male bighorn sheep using 12 herd datasets from across the western United States that had horn growth and disease data. Disease resulted in 12–35% reduction in increment (yearly) length and 3–13% reduction in total horn length in exposed individuals. The disease effect was prolonged when pathogens continued to circulate in sheep populations. Further, disease likely delays the age at which horns reach ¾-curl and prevents achievement of full-curl. This is further evidenced with 6 of the 12 herds experiencing an increase in average age at harvest following die-off events. |
| Keywords: | bighorn sheep horn size Mycoplasma ovipneumoniae Ovis canadensis pneumonia secondary sexual characteristics wildlife disease wildlife management |