Reduced breeding densities associated with spatially concentrated harvest of willow ptarmigan in Alaska

Understanding the effects of harvest on wildlife populations is fundamental to theoretical wildlife science and applied wildlife management. Demographic compensation plays a key role in models of wildlife population dynamics and in developing harvest strategies. The degree and form of compensation in a given population depend on its particular ecological and life-history characteristics and the timing and magnitude of harvest. Consequently, substantial variation exists in compensatory potential among populations, and it cannot be assumed that a particular population is capable of compensating for harvest. This underscores the importance of population-specific assessments of responses to harvest. We examined the hypothesis that concentrated hunting pressure in road-accessible areas reduces subsequent breeding season densities of willow ptarmigan (Lagopus lagopus), in Alaska, USA, 2014-2015. We estimated breeding season densities of ptarmigan territories at sites within hunted access corridors and at remote sites with little or no hunting pressure. Estimated densities were substantially higher at remote sites (5.3-5.8 territories/km(2)) than at accessible sites (1.8-3.7 territories/km(2)). Two habitat-proxy covariates, distance to water and elevation (modeled as smoothed effects), exhibited strong associations with the density of ptarmigan territories. These results suggest a possible additive effect of spatially concentrated harvest on local breeding densities.