Long-term changes in migratory patterns of elk (Cervus canadensis) in the southern Rocky Mountain Trench of British Columbia, Canada

• Author / Creator

  Mulligan, Kelly

• Migration can be described as a round-trip movement between distinct ranges and is thought to be a response to a spatiotemporal variation in resources. Large vertebrate herbivores such as ungulates often migrate to track seasonal variability in high quality forage and reduce predation risk. Recent evidence indicates ungulate migration is being lost globally, which has been attributed to human disturbances such as agriculture, barriers to movement including expanding human infrastructure, and recovering predator populations. In the southern Rocky Mountain Trench in British Columbia concerns over a reduction in the migratory portion of an elk (Cervus canadensis) population were concomitant with the recovery of wolves (Canis lupus), increasing grizzly bear (Ursus arctos) populations, increased wildlife exclusion fencing, and increasing forest encroachment. This work quantified Rocky Mountain Trench elk migratory decline by determining the ratio of migrant to resident elk (M:R) across three periods (1987–1993, 2007–2010, and 2014–2018). We then explored what might be driving this migratory decline by qualitatively assessing whether M:R trends were consistent with predictions from five non-mutually exclusive hypotheses––competitive release, social fence, foraging areas, agriculture subsidy, and human shield––postulated to influence elk migration over time. Finally, we compared trends in habitat suitability of high elevation (≥ 1,200 m) migrant and low-elevation (< 1,200 m) resident summer ranges using resource selection functions. Our results demonstrate that the proportion elk migrating in summer declined from 80% in 1987–1993, to 51% in 2007–2010, then to 39% in 2014–2018. Increasing elk residency was most consistent with the human refuge hypothesis, as elk residency on low elevation, human-dominated landscapes increased as both wolf and grizzly bear abundance increased. Both migrant and resident elk avoided areas with major roads and showed selection for natural herb-shrub areas and early seral vegetation found in areas of wildfire and timber harvest. Habitat suitability declined throughout the study for both migrant and resident elk, with a greater decline on migrant ranges. Results from this study will help managers address the challenges of restoring elk migrations amidst the challenges presented by predator recovery and on-going land use changes.

• Subjects / Keywords

  • ungulate
  • migration
  • elk
  • montane
  • disturbance
  • resource selection
  • human shield
  • disturbance
  • temporal
  • Cervus canadensis

• Graduation date

  Spring 2021

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-ygyq-6606

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.