Breeding migrations by bighorn sheep males are driven by mating opportunities

In some species where male mating success largely depends on intrasexual competition, males can adopt migratory or resident strategies to seek breeding opportunities. The resulting mixture of resident and migrant tactics within a population can have important ecological, genetic, and evolutionary consequences for metapopulations. Bighorn sheep Ovis canadensis males establish a linear dominance hierarchy that influences their mating tactics. Some males perform breeding migrations during the pre‐rut and rut to seek mating opportunities, but little is known about these seasonal movements. We analyzed presence/absence data for 62 marked bighorn males during six mating seasons (20–32 males/year) in the Sheep River Provincial Park, Alberta, Canada, where hunting was not allowed. On average, about half of males left their natal population to rut elsewhere. The proportion of males leaving (yearly range 15%–69%) increased as the number of resident mature males increased and the populational sex ratio decreased, with fewer females during the pre‐rut. Among those leaving the park, 24% did so in October, while the trophy sheep hunting season was open. Detailed monitoring of breeding migrations in protected populations could inform management strategies to limit evolutionary impacts of hunting, which can alter size‐dependent mortality and create artificial pressures driving changes on heritable traits. In bighorn sheep, Ovis canadensis, some males undertake breeding migrations during the pre‐rut and rut periods to seek mating opportunities. We explored the individual and populational determinants of male migratory rutting tactics and the timing of these movements in the fall. As male undertaking breeding migrations are more at risk of getting harvested, especially when they move out of protected areas, our results have implications for wild sheep management as gene flow may be reduced and insufficient to limit hunting‐induced artificial selection on horn size.