The Role of Human Altered Landscapes and Predators in the Spatial Overlap Between Moose, Wolves, and Endangered Caribou

• Author / Creator

  Anderson, Meghan Samantha

• Human altered landscapes can cause the endangerment or extinction of a species, not only by a direct loss of habitat but by altering predator-prey relationships. Predators can drive prey to extinction when the density of the predator becomes subsidized by another abundant, alternate prey. Such indirect species interactions are termed “apparent competition” and are increasingly being linked to species endangerment. The mechanism behind apparent competition may be differences between the prey species in reproductive success, niche overlap, or differences in ability to escape predation. This study focused on a case of apparent competition between moose (Alces alces), wolves (Canis lupus), and endangered mountain caribou (Rangifer tarandus caribou) in the Columbia Mountains of British Columbia. The southern mountain population of caribou escape predation by residing at high elevations most of the year. However, when moose move into caribou habitat in the summer wolves often follow, exposing caribou to greater predation risk. I examined two hypotheses why moose move into caribou habitat in the summer. First, I examined the hypothesis that human-caused early-seral vegetation available in mountain caribou summer habitat attracts moose. I examined this hypothesis using four predictions: i) moose forage will be more abundant in high-elevation cutblocks compared to other habitats at high and low elevations, ii) moose preferentially select for cutblocks at high elevation relative to low-elevation cutblocks, iii) when moose are at high elevations they will be closer to cutblocks than would be expected by random, iv) the amount of cutblocks at high elevations in a moose home range will be positively related to the amount of time moose spend at high elevations. I found my second prediction was supported; moose did select for cutblocks at high elevations. However, the remaining predictions were not supported: moose forage was not more abundant in high-elevation cutblocks, moose at high elevations were not located closer to cutblocks than would be expected by random, and the proportion of cutblocks in a moose home range at high elevations was not positively related to the amount of time moose spend at high elevations. While moose highly select for human-caused early-seral habitat, when they are at high elevations moose spend the majority of their time in old-growth forests, suggesting that moose forage in old-growth habitat at high elevations as well as early-seral. Given the mixed results and overall lack of support for the hypothesis I conclude that human-caused early-seral vegetation available in caribou summer habitat does not attract moose to high elevations in the summer. Next I examined the hypothesis that in the summer, moose are exposed to less predation risk at high elevations and that moose move into mountain caribou habitat in response to predation risk. I examined this hypothesis using three predictions: i) the spatial overlap between wolves and moose will decrease during the summer, ii) moose will be exposed to lower predation risk at high elevations compared to low elevations in their home ranges, iii) moose will select for areas of low predation risk. Two of my predictions were supported and one received partial support. Moose were able to distance themselves from wolves in the summer by moving upslope and as a result reduced their exposure to predation risk. Moose exposure to wolf predation was most effectively reduced in the early summer when wolves were constrained to valley bottoms because of denning activities. Finally, moose selected areas of intermediate predation risk and avoided areas of high predation risk. Areas of low predation risk, such as, the alpine, provide little food and cover and were avoided by moose. The results support the hypothesis that moose move into mountain caribou habitat in the summer to avoid predation. I conclude that the basis of mountain caribou recovery will continue to be practices aimed at reducing predator populations and the amount of early-seral vegetation to reduce the density of moose.

• Subjects / Keywords

  • Caribou
  • Wolves
  • Moose

• Graduation date

  Fall 2014

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R31Z42202

• 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.