Mating tactic influences body condition loss in Rocky Mountain bighorn rams (Ovis canadensis)

In polygynous mating systems, males often employ alternative mating tactics to enhance reproductive success. In Rocky Mountain bighorn sheep, the primary tactics are coursing, involving mating chases, and tending, involving mate guarding. While both tactics are energetically costly and can diminish body condition, it remains unclear whether the associated costs significantly differ and to what extent. Our study investigated the impact of mating tactics, specifically the proportion of time allocated to each, on body condition loss during the rutting season in bighorn sheep. Using a non-invasive photographic method to estimate body condition loss, we found that the proportion of time a male spent tending significantly correlated with body condition loss. In contrast, the percentage of time spent coursing did not show a significant effect. Age was associated with the choice of tactic, with younger males predominantly coursing, older males primarily tending, and some intermediate-aged males employing both tactics concurrently. Despite the higher energetic costs, our results reveal the flexibility in tactic usage and indicate that tending, while demanding, is a high-cost, high-gain strategy, as tending rams are known to sire more offspring.