An adaptive approach to endangered species recovery based on a management experiment: reducing moose to reduce apparent competition with woodland caribou

  • Author / Creator
    Serrouya, Robert D
  • Species that are rare yet widely distributed are among the most challenging to conserve. The mountain ecotype of woodland caribou (Rangifer tarandus) is declining because of apparent competition with non-caribou ungulates (NCU) such as moose (Alces alces). I experimentally assessed whether reducing NCU could facilitate caribou recovery by taking advantage of a government policy to reduce moose abundance with increased hunting. First, I used microsatellite markers to evaluate the evolutionary significance of the mountain ecotype, and determined whether previously identified subpopulations were demographically distinct. I found that subpopulation structure was mainly caused by genetic drift in small populations. The demographic isolation of many subpopulations suggests that they are appropriate as management units for recovery planning. I then developed an ecological target for recovering caribou by estimating the abundance of moose that would have occurred in the absence of forest harvesting. I incorporated this target into predator-prey equations to make predictions about the risks and benefits to caribou. Predictions suggest that reducing NCU without reducing predators could negatively impact caribou. The predicted impact was greater if there was a time lag of the predators’ numerical response, but gradually reducing NCU could mitigate this impact. Once the moose reduction was initiated in the field, the decline in moose numbers was greater than could be explained by the hunting treatment alone. I contrasted several hypotheses to explain the rate of decline, including density dependent, depensatory, or compensatory predation by wolves (Canis lupus). I found that depensatory predation best explained the moose decline, but hunting was the catalyst. Reducing moose appeared to reduce wolf numbers, with dispersal the likely mechanism. Remaining wolves spent more time in caribou habitat, but based on scat and kill-site investigations, there was no evidence that wolves shifted their diet to caribou. In the treatment and reference areas, the caribou response was mixed, with the larger subpopulations stabilizing but smaller ones continued to decline. By combining theoretical predictions with empirical manipulations I conclude that reducing NCU and predators concurrently is a prudent approach to recover caribou. Few broad-scale manipulations exist to recover endangered species, but are needed to evaluate recovery options.

  • Subjects / Keywords
  • Graduation date
    Fall 2013
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • 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.
  • Language
  • Institution
    University of Alberta
  • Degree level
  • Department
  • Specialization
    • Ecology
  • Supervisor / co-supervisor and their department(s)
  • Examining committee members and their departments
    • Nielsen, Scott (Renewable Resources)
    • Murray, Dennis (External, Trent University)
    • McLellan, Bruce N. (British Columbia Forest Service, Research Branch)
    • Bayne, Erin (External, Biological Sciences)
    • Seip, Dale (British Columbia Ministry of Environment)
    • Lewis, Mark (Biological Sciences)