Habitat and herbivore density: Response of mule deer to habitat management

Abstract

The suite of demands competing for wildlife management funds necessitates direct assessment of management decisions, especially when these decisions have direct costs, as well as tangible opportunity costs. We conducted a mark–resight study that estimated mule deer (Odocoileus hemionus) density across multiple study units in southwest Colorado that had been exposed to different intensities of habitat treatments. Our treatments were comprised of common habitat management techniques including hydro‐axe and roller‐chopper disturbances as well chemical control of weeds and reseeding with desirable mule deer browse species. Reference study units received no habitat management treatments. Total deer densities varied between 20–84 deer/km2 in southern study units and 4–12 deer/km2 in northern study units. We did not observe a consistent pattern of higher deer density on advanced treatment study units despite it being the primary hypothesis of the study. We observed a wide range of variation in deer density among years. Resighting probabilities (range 0.070–0.567) were best modeled as an interactive function of study unit and year, although sampling method was also influential. We recommend that if population density is to be used as a population response variable, it be used in tandem with other, possibly more sensitive parameters such as overwinter survival or late winter body condition. © 2014 The Wildlife Society.

Habitat Use Informs Species Needs and Management: A Reply to Maestas et al.

“…Removal of juniper on mule deer winter range in Colorado, USA, followed by reseeding of preferred mule deer forage was correlated with increased body condition of adult females (Bergman et al 2014b) and overwinter juvenile survival (Bergman et al 2014a). Despite these demographic responses, treatments did not translate to observable changes in mule deer density (Bergman et al 2015). Collectively, these studies highlight the importance of nutritional limitations for mule deer on winter range.…”

Mule deer and energy development—Long‐term trends of habituation and abundance

“…Although it may be possible to improve the quality of winter range in areas with longer growing seasons or where tree removal can promote new shrub growth (e.g. Bergman, Doherty, White, & Freddy, ), few viable options exist for improving winter ranges that are semi‐arid at high elevation and dominated by sagebrush (Korfanta et al., ). Notwithstanding range expansion or habitat improvement to offset habitat loss, we would expect population size to decline through density‐dependent mechanisms (sensu Bartmann, White, & Carpenter, ; Bowyer, Bleich, Stewart, Whiting, & Monteith, ).…”

Multiscale models of habitat use by mule deer in winter

“…Adult mule deer have adapted to losing weight in winter (Torbit et al ), but during severe winters, adult survival declines, and given the high sensitivity of ungulate population growth to adult survival (Gaillard et al ) populations also decline (Loveless , Gilbert et al , Hurley et al ). This is particularly true if sufficient winter range habitat is not available (Wallmo , Bergman et al ). Further, fawn survival has increased in areas where supplemental forage was provided during winter (Baker and Hobbs , Bishop et al ), indicating that a lack of abundant and high quality forage on winter range could be a factor limiting mule deer population growth.…”