Effects of harvest on wolf social structure, population dynamics, and viewing opportunities in national parks

Abstract

Management of gray wolves (Canis lupus) in and adjacent to Denali National Park and Preserve (DNPP) is complex. Wolves that live primarily within the park, where they are protected from harvest, often range across the boundary of the park where harvest of wolves is legal. Protection of wolves within the park provides for wolf viewing opportunities along the Denali Park Road for tens of thousands of visitors annually. Additionally, there is interest in maintaining wolf harvest opportunities adjacent to the park. The objectives for wolf viewing and harvest have been perceived as in direct conflict, but quantitative analysis of the relationship was lacking. Harvest of wolves is a highly contentious conservation and management issue worldwide, with unknown population-level consequences. The impact of the loss of reproductive individuals (breeders) may be particularly important to wolf pack structure, reproduction and population dynamics. I evaluated the effect of breeder loss on social stability, recruitment and population growth of wolves in DNPP and found that breeder loss preceded 77% of cases (n = 53) of pack dissolution from 1986 to 2012. Packs were more likely to dissolve if a female or both breeders were lost and pack size was small. Harvest of breeders increased the probability of pack dissolution, likely because the timing of harvest coincided with the breeding season of wolves. Breeder mortality and pack dissolution had no significant effects on immediate or longer-term population dynamics. I examined the effect of legal harvest of wolves along the boundaries of DNPP and Yellowstone (YNP), on wolf viewing opportunities within the parks during peak tourist season. Although sightings were largely driven by wolf population size and proximity of den sites to roads, sightings in both parks were significantly reduced by harvest. Sightings in YNP decreased by 31% following years with harvest of a wolf from a pack and sightings in DNPP decreased by 57% during the absence of a harvest buffer zone relative to years with the buffer. Controlling for variables influencing both the probability of wolf presence near the road and the detection of wolves, we found that the presence of a wolf harvest buffer zone adjacent to the park increased wolf sightings along the Denali Park Road. The effect of the harvest buffer on sightings was similar in magnitude to an increase in pack size by two wolves or more than a twofold decrease in masking vegetation. These results suggest that harvest adjacent to park has the potential to substantially reduce wolf sightings. Harvest of wolves adjacent to protected areas can reduce sightings within those areas despite minimal impacts on the size of protected wolf populations. Consumptive use of carnivores adjacent to protected areas may therefore reduce their potential for non-consumptive use, and these tradeoffs should be considered when developing regional wildlife management policies.