Exotic plant management often begins only after introduced taxa become widespread and problematic. Control efforts at this stage have a higher potential to lead to unintended outcomes in native systems. We explored the impacts of ongoing invasive plant management on a native ectotherm, the copperhead (Agkistrodon contortrix), in a landscape heavily impacted by multiple nonnative plant species. We found that habitats undergoing invasive plant control are preferred by snakes over other available habitats, but these individuals are at greater risk of injury and mortality owing to policy-driven methods of control. At the same time, we show that management can reverse invader impacts, notably reclaiming thermoregulatory opportunities for ectotherms, thus offering benefits as well as challenges for such animals. This introduces a key dilemma for conservation as invasive plant management can reclaim critical resources while policy-driven control methods can undermine the success of these efforts. We outline several simple and direct solutions that may easily be incorporated into management plans.

Exotic invasive plants can alter ecosystem structure and function, yet there is a paucity of evidence regarding broadly applicable mechanisms. We hypothesized that denser growth patterns characteristic of exotic invasive plants lead to a common effect of reduction and homogenization of environmental temperatures and that these alterations compromise thermal quality of habitat for ectotherms. We quantified thermal regimes within native and exotic plant-dominated habitats, including monocultures of 11 exotic species as well as stratified mixed-exotic habitats in a temperate forest landscape in the eastern US. Exotic plant-dominated habitats exhibited reduced and less variable temperature compared to their native counterparts, with stratified mixed-exotic habitats exhibiting the lowest temperatures overall and exotic shrubs (six species) the lowest as a structural group. Thermal effects were extended beyond the growing season of native vegetation owing to extended leaf phenology of exotic woody species. To demonstrate that these effects can alter environmental cues and adversely impact native species, we used a 4-year radiotelemetry study and laboratory thermal preference trials to relate habitat thermal quality to multiscale resource selection by a native snake, Agkistrodon contortrix. To further test the effect of vegetation structure and the efficacy of targeted management, we removed exotic foliar cover from eight 400m(2) plots. Radio-tagged snakes avoided exotic vegetation at multiple spatial scales. In contrast to previous studies of A.contortrix, snakes exhibited preference for sites composed of higher native vegetation density and height. Response to exotic foliage removal was also rapid - including use of sites during gestation and parturition. Together with other recent studies, our results suggest a direct, non-trophic effect that is common to a broad range of exotic invasive plant species in a variety of ecological contexts. We further offer a mitigation technique that may be implemented when large-scale control or eradication is not cost-effective or ecologically sound.

Parks and outdoor recreation areas often struggle to balance management for outdoor recreation with the protection of native flora and fauna. Additional complications can arise for land managers when recreation occurs in areas shared with wildlife that are perceived by humans to be dangerous. Despite these issues, many parks may inadvertently increase the potential for human-wildlife encounters through the creation of artificial forest gaps used for recreational purposes. We determined the potential for human encounters with venomous copperhead snakes (Agkistrodon contortrix) at a recreational park in southern Indiana before and after several simulated closures of recreational forest gaps. By restricting human access to artificial forest gaps, encounters with copperheads could be reduced by 1.5 to 8 times the observed encounter rate. We discuss conservation implications and provide suggestions for recreational park managers facing related concerns of human-wildlife encounters.