Dataset used for: Breeding migrations by bighorn sheep males: searching for mates increases vulnerability to hunting

In some species where male mating success largely depends on intrasexual competition, males can adopt migratory orresident strategies to seek breeding opportunities. The resulting mixture of resident and migrant tactics within a population can have important ecological, genetic and evolutionary consequences at the metapopulation level. 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 analysed 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.