Elk resource selection and indicator species analysis

Resource selection by animals varies depending on spatial and temporal
context, thus it is important to account for these factors when conducting
studies that examine this behavior relative to the availability and
distribution of resources.  Many resource selection studies
combine fine-scale animal location data obtained using Global Positioning
System (GPS) technology and coarse-scale, remotely sensed, spatial layers.
Fewer studies combine fine-scale animal location data with vegetation data
collected in the field, which can identify important fine-scale drivers of
resource selection. Understanding fine-scale resource selection of
ungulates inhabiting regions dominated by closed-canopy forests may
provide important information regarding management actions that improve
habitat quality. From April 2021–August 2022, we conducted vegetation
surveys at locations (n = 1,294) used by 39 GPS-collared elk (Cervus
canadensis) and at paired random locations (n = 2,509) available to elk.
We used conditional logistic regressions to compare seasonal (spring,
summer, fall, winter) vegetation characteristics between used and
available locations. We also conducted a species indicator analysis to
compare plant species found at used and available locations during peak
foraging periods (dawn/dusk). Regardless of season, the probability of use
by elk increased as tree basal area (m2/ha) decreased, and the presence of
herbaceous plants increased. Clovers (Trifolium spp.)
were indicators of locations used by elk during primary foraging
periods regardless of season. Other plants that were indicators of
locations used by elk during at least one season included purple-crown
vetch (Securigera varia), bird’s foot-trefoil (Lotus corniculatus), and
black medick (Medicago lupulina). This research highlights the importance
of managed openings, ecotones, and other communities characterized by
reduced tree cover and increased herbaceous plants to meet the foraging
needs of elk in landscapes dominated by closed-canopy forests. Creating
and maintaining managed herbaceous openings and restoring open-forest
communities will likely facilitate elk population growth and expansion.