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Disease and secondary sexual traits: Effects of pneumonia on horn size of bighorn sheep

January 5, 2022

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.

Citation Information

Publication Year 2022
Title Disease and secondary sexual traits: Effects of pneumonia on horn size of bighorn sheep
DOI 10.1002/jwmg.22154
Authors Alynn Marie Martin, John T. Hogg, Kezia R. Manlove, Tayler N LaSharr, Justin M. Shannon, Douglas E. McWhirter, Hollie Miyasaki, Kevin L. Monteith, Paul C. Cross
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Wildlife Management
Index ID 70227317
Record Source USGS Publications Warehouse
USGS Organization Northern Rocky Mountain Science Center