Variation in elk response to roads by season, sex, and road type

Abstract

Despite the near universal recognition that roads negatively affect wildlife, the mechanisms that elicit animal responses to roads are often ambiguous or poorly understood. We conducted a multi-year, multi-season study to assess the relative influence of roads on elk (Cervus elaphus) in a human-dominated landscape in South Dakota. We evaluated the effects of habitat covariates including security cover, forage quality, distance to roads (primary, secondary, and tertiary), and visibility from roads at the home range scale. We radio-collared 28 elk (21 adult females and 7 adult males) and calculated seasonal (winter, spring, summer, and autumn) utilization distributions (UDs). We assigned habitat covariates to use percentiles within the UDs (1% increments; from 1 to 98 percentiles) and used spatially explicit mixed linear regression to model the relationship between use percentile and habitat covariates. For each season and sex, we evaluated 15 candidate models and used Akaike's Information Criterion weights (v i ) to identify top-ranking models. We plotted influential coefficients from these models with 95% confidence intervals to examine the magnitude of effects. Our analysis revealed fundamental differences in response to roads, by road type, between sexes, and across seasons. Male elk established home ranges near roads devoid of vehicle traffic in winter, spring, and autumn. In summer, coinciding with peak vehicle traffic levels, male elk reduced their use of habitat that was both visible from and close to primary roads. Female elk subherds similarly responded to primary roads in spring and autumn, during times of year when they were calving and mating, respectively. In spring and summer, female elk subherds selected habitat near roads that were closed to vehicle traffic. Forage quality and security cover were influential in the periphery (>50th use percentile) of elk home ranges, whereas road covariates were more influential towards the core of elk home ranges. This analysis further demonstrates the utility of visibility from road metrics and suggests that the retention of vegetation structures that screen visibility potential from roads could be important components of elk management strategies. ß 2012 The Wildlife Society.

Elk resource selection at parturition sites, Black Hills, South Dakota

“…Rugged topography can provide a buffer from roads and potential human disturbance in open habitats (Edge and Marcum , Rowland et al ). Distance to roads can be a powerful predictor of elk resource selection (Blan and West , Millspaugh et al , Stubblefield et al , Sawyer et al , Montgomery et al ). Higher levels of physiological indicators of stress, such as fecal glucocorticoids, have been observed in elk exposed to increased road density and traffic on roads during spring and summer in the Black Hills (Millspaugh et al ).…”

“…Our study population has been declining since 2006, which is of concern for game managers and hunters (South Dakota Department of Game, Fish, and Parks ). Some areas are heavily influenced by high road densities that average >2.1 km/km 2 (Rumble et al , Stubblefield et al , Montgomery et al ) and human recreation that could negatively influence calving (Shively et al , Black Hills National Forest ). Predation, primarily from puma on elk calves, resulted in ≤27% annual survival of calves (Lehman ), so we hypothesized that predation was important in decisions of resource selection of parturition sites by female elk.…”

Mapping resource selection functions in wildlife studies: Concerns and recommendations

“…We selected the most parsimonious model using Akaike’s Information Criterion (AIC). Environmental covariates considered in model development included two land cover types: forested and non-forested (2010 Montana Spatial Data Infrastructure land cover dataset; http://geoinfo.montanastatelibrary.org/data/msdi/landuse/), elevation (national elevation dataset; http://ned.usgs.gov/), slope, aspect categorized as southerly (134 – 224°) and not southerly (0 – 135°, 225 – 360°), distance to primary, secondary and tertiary roads following Montgomery et al (2013), and wolf predation. We standardized all continuous variables to allow for a direct comparison between model coefficients.…”

Space use and resource selection by foraging Indiana bats at the northern edge of their distribution

“…Through the RUF calculation we used the height (z-value) of the UD at each grid point as the response variable in a multiple regression analysis that in cluded combinations of predictor variables that represent the hypotheses outlined above (Marzluff et al 2004). Prior to analysis, we clipped each bat UD by its 99% volume contour and re-standardized the values of each bat UD into 100 UD percentiles, so that the probability of use was on a scale of 0 to 100, with 100 representing the highest probability of use (Ja chow ski et al 2013, Montgomery et al 2013). We evaluated support for our models ( (Marzluff et al 2004, Jachowski et al 2011, and then projected predicted foraging use across the larger Fort Drum landscape.…”