1. Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
2. Alberta Department of Sustainable Development, Fish and Wildlife Division, Box 1059, Canmore, Alberta T0L 0M0, Canada
3. Montana Conservation Science Institute, Missoula, Montana 59803, USA
4. Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada
5. Département de biologie, Université de Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada

Correspondence to: David W. Coltman¹ Email: d.coltman@sheffield.ac.uk

Abstract

Phenotype-based selective harvests, including trophy hunting, can have important implications for sustainable wildlife management if they target heritable traits^{1, 2, 3}. Here we show that in an evolutionary response to sport hunting of bighorn trophy rams (Ovis canadensis) body weight and horn size have declined significantly over time. We used quantitative genetic analyses, based on a partly genetically reconstructed pedigree from a 30-year study of a wild population in which trophy hunting targeted rams with rapidly growing horns⁴, to explore the evolutionary response to hunter selection on ram weight and horn size. Both traits were highly heritable, and trophy-harvested rams were of significantly higher genetic 'breeding value' for weight and horn size than rams that were not harvested. Rams of high breeding value were also shot at an early age, and thus did not achieve high reproductive success⁵. Declines in mean breeding values for weight and horn size therefore occurred in response to unrestricted trophy hunting, resulting in the production of smaller-horned, lighter rams, and fewer trophies.