Microhabitat Use by Disjunct Common Five-Lined Skink (Plestiodon fasciatus) Populations at Their Northwestern Range Extent

Habitat management activities commonly are predicated on responses of vegetation and charismatic wildlife groups such as birds and mammals, which can be inadequate proxies for reptile conservation without evidence of their mutual benefit. Reptiles require focused assessments because they typically are underrepresented in research and conservation. Further, populations at their species' range limits may be more vulnerable to extirpation due to different selection pressures. We examined microhabitats of a northern, disjunct population of Common Five-lined Skinks (Plestiodon fasciatus) in the Upper Minnesota River Valley of Minnesota, USA, to quantify key habitat management thresholds better. On four sites, we established plot grids representing a range of vegetation, terrain, canopy, and ground-cover variables. We systematically checked cover objects to document P. fasciatus and measured habitat characteristics at each sampling plot within these grids. Using N-mixture and generalized linear mixed models, we studied skink abundance relative to variables associated with P. fasciatus habitat that also are likely to be directly manipulated by land managers. These two modeling techniques produced very similar results. They showed that P. fasciatus abundance was positively associated with large down woody debris (.15-cm diameter), and negatively associated with canopy closure and herbaceous cover greater than 75%. Models also showed negative associations with stem density of a nonnative shrub, Common Buckthorn (Rhamnus cathartica), and slightly positive associations with a native shrub, Smooth Sumac (Rhus glabra). The effects of shrub density were more pronounced when we assessed pre- and posttreatment effects of shrub management. Posttreatment we observed 97–188% increases in skink detections under cover objects. We developed management targets for each of these habitat traits that were important correlates of P. fasciatus abundance. Our findings will help inform development of best management practices for P. fasciatus in this and potentially other similar northern landscapes. We identified management and research implications and recommended effectiveness monitoring to support adaptive management within a changing landscape and climate.