Effects of bull elk demographics on age categories of harem bulls

Many management strategies for elk (Cervus elaphus) emphasize increasing numbers of mature bulls in the population. These strategies are usually assumed to enhance productivity via increased breeding by mature bulls. I compared age classes of harem bulls during the peak of the rut under 4 bull harvest strategies that resulted in different bull:cow ratios, mature bull:cow ratios, bull mortality rates, and proportions of mature bulls in the autumn (pre-hunting season) population. Proportions of harems held by differing age classes of bulls [mature (P<0.001), juvenile (P=0.002), and yearling (P=0.005)] differed by harvest strategy. Proportions held by mature bulls increased with increasing restrictions on bull harvest and were related most strongly (r2=0.84-0.92) to number of mature bulls:cow. For harvest strategies studied here (e.g., unharvested, aselective, or selective of older bulls), mature bulls tended >84% of harems only in populations where mature bull:cow ratios exceeded 21:100 in the autumn population. Interaction of mature bull ratios in the autumn population, harem size, and bull selectivity in the harvest strategy must be considered if increased breeding by mature harem bulls is a management goal.