, Volume 166, Issue 3, pp 593–605 | Cite as

From process to pattern: how fluctuating predation risk impacts the stress axis of snowshoe hares during the 10-year cycle

  • Michael J. Sheriff
  • Charles J. Krebs
  • Rudy Boonstra
Population ecology - Original Paper


Predation is a central organizing process affecting populations and communities. Traditionally, ecologists have focused on the direct effects of predation—the killing of prey. However, predators also have significant sublethal effects on prey populations. We investigated how fluctuating predation risk affected the stress physiology of a cyclic population of snowshoe hares (Lepus americanus) in the Yukon, finding that they are extremely sensitive to the fluctuating risk of predation. In years of high predator numbers, hares had greater plasma cortisol levels at capture, greater fecal cortisol metabolite levels, a greater plasma cortisol response to a hormone challenge, a greater ability to mobilize energy and poorer body condition. These indices of stress had the same pattern within years, during the winter and over the breeding season when the hare:lynx ratio was lowest and the food availability the worst. Previously we have shown that predator-induced maternal stress lowers reproduction and compromises offspring’s stress axis. We propose that predator-induced changes in hare stress physiology affect their demography through negative impacts on reproduction and that the low phase of cyclic populations may be the result of predator-induced maternal stress reducing the fitness of progeny. The hare population cycle has far reaching ramifications on predators, alternate prey, and vegetation. Thus, predation is the predominant organizing process for much of the North American boreal forest community, with its indirect signature—stress in hares—producing a pattern of hormonal changes that provides a sensitive reflection of fluctuating predator pressure that may have long-term demographic consequences.


Cortisol Population cycles Low phase Maternal effects Sublethal effects 



We thank A.T. Sheriff, K. Pieczora, S. Mitford and E. Hofer for their contributions to this project. The Natural Sciences and Engineering Research Council of Canada, the Department of Indian Affairs and Northern Development, the EJLB Foundation, and the Arctic Institute of North America all supported this research. We thank Andrew Williams and the Arctic Institute of North America, University of Calgary, for providing facilities at Kluane Lake. The University of British Columbia Animal Care Committee approved all procedures in accordance with the guidelines of the Canadian Council for Animal Care.


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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • Michael J. Sheriff
    • 1
    • 2
  • Charles J. Krebs
    • 2
  • Rudy Boonstra
    • 1
  1. 1.Centre for the Neurobiology of StressUniversity of Toronto ScarboroughTorontoCanada
  2. 2.Department of ZoologyUniversity of British ColumbiaVancouverCanada

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