Forests of the Rocky Mountains (USA and Canada) have experienced a large‐scale bark‐beetle (Dendoctronus ponderosae) epidemic that has led to widespread mortality of pine trees, followed by structural and compositional changes to the forest. The millions of dead trees resulting from this event likely have an effect on ecosystem processes, but currently those effects are mostly unclear. Changes to forest canopy and understory structure are likely to affect behavior and space use of large ungulates as forage abundance, thermal cover, and locomotive costs are presumably altered. We developed and tested hypotheses for how resource selection in summer of female elk (Cervus canadensis; n = 47; 2012–2016), the primary large mammal in our study area, was influenced by changes in canopy, understory vegetation, and downed logs in bark‐beetle affected forest in south‐central Wyoming, USA. We employed global positioning system (GPS) technology, an imagery‐derived land cover classification specifically depicting beetle‐affected forest, and on‐the‐ground forest measurements to develop resource and step selection functions. At the study area scale, elk avoided beetle‐killed forest during nearly all parts of the day and selected for intact conifer forest during the day. At the micro‐habitat scale, as canopy cover decreased in beetle‐killed areas, there was a concomitant increase in grass biomass and downed logs. Nevertheless, while in the forest, elk did not alter resource selection relative to changes in understory vegetation or downed logs. The boost in forage abundance within beetle‐killed areas was insufficient to overcome the presumed increases in energy expenditures associated with locomotion and thermoregulation in beetle‐killed forests. The bark‐beetle epidemic has altered how elk use the landscape and has resulted in a potential loss of forest habitat that elk use during the day. Our results indicate that habitat treatments (i.e., fire or harvest) that remove standing dead trees and downed logs in beetle‐killed forest would further facilitate understory growth while reducing the locomotion costs associated with foraging in beetle‐killed forest. © 2019 The Wildlife Society.
For nearly 2 decades, the forests of the Rocky Mountains in the United States experienced a bark‐beetle (Dendoctronus ponderosae) epidemic. The number of dead and falling trees from this epidemic likely will affect how elk (Cervus canadensis) and hunters use the forest and their interactions. Downed trees potentially create a component of refuge habitat that could affect the effectiveness of hunting to regulate abundance of growing elk populations. We evaluated how forests affected by bark beetles in south‐central Wyoming, USA, influenced resource selection of 50 female elk and 374 hunters in 2012–2016, and interactions between elk and hunters. We employed global positioning system (GPS) technology on elk and hunters, and developed a satellite‐derived land classification specifically depicting beetle‐affected forests. We tested the predictions that elk would increase use of beetle‐killed areas from summer to the hunting season, and that hunters would avoid beetle‐killed areas regardless of elk use. Elk increased use of beetle‐killed areas during hunting seasons as did hunters during the archery season; however, during the rifle season, hunters avoided beetle‐killed areas. Nevertheless, during the rifle season, areas of beetle‐kill with a high probability of elk occurrence dampened the aversion hunters had towards beetle‐killed areas. Therefore, in contrast to our expectations, forests that have been altered by the bark‐beetle epidemic may only function marginally as a refuge for elk. Our study area was at the beginning of the tree‐fall phase (i.e., ~3–7 yr after peak infestation) of the bark‐beetle epidemic; thus, future research efforts should focus on how a continued increase in downed trees will influence interactions between elk and hunters. At current levels of tree fall, however, beetle‐kill should not limit the ability of managers to regulate elk herds through harvest. © 2020 The Wildlife Society.
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