Changes in horn size of Stone's sheep over four decades correlate with trophy hunting pressure

Selective harvest may lead to rapid evolutionary change. For large herbivores, trophy hunting removes males with large horns. That artificial selection, operating in opposition to sexual selection, can lead to undesirable consequences for management and conservation. There have been no comparisons of long-term changes in trophy size under contrasting harvest pressures. We analyzed horn measurements of Stone's rams (Ovis dalli stonei) harvested over 37 years in two large regions of British Columbia, Canada, with marked differences in hunting pressure to identify when selective hunting may cause a long-term decrease in horn growth. Under strong selective harvest, horn growth early in life and the number of males harvested declined respectively by 12% and 45% over the study period. Horn shape also changed over time: horn length became shorter for a given base circumference, likely because horn base is not a direct target of hunter selection. In contrast, under relatively lower hunting pres...选择性收获可能引发快速的进化改变。对于大型植食动物而言，战利品狩猎会移除拥有硕大犄角的雄性个体。这种与性选择相悖的人工选择，可能给种群管理与保护工作带来不利后果。目前尚无针对不同狩猎压力下战利品尺寸长期变化的对比研究。我们分析了加拿大不列颠哥伦比亚省两个狩猎压力差异显著的大型区域内，37年间被狩猎的斯通大角羊（Ovis dalli stonei）的犄角测量数据，以明确选择性狩猎何时会导致犄角生长的长期衰退。在高强度选择性狩猎的区域内，研究周期内雄性个体幼年时期的犄角生长量以及被狩猎的雄性数量分别下降了12%和45%。犄角形态也随时间发生了改变：在基座周长固定的情况下，犄角长度变得更短，这可能是因为猎手的狩猎目标并未直接指向犄角基座。与之相对，在相对较低的狩猎压力下...