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Snowshoe hare demography and behaviour during a cyclic population low phase

University of British Columbia

Snowshoe hares, Lepus americanus, undergo a ten-year population cycle. I examined whether hares respond behaviourally to predators, and whether hare behaviour influenced population dynamics. If behaviour reduces hares' condition and fecundity, that could explain why the low phase lasts two to four years. I used a factorial manipulation of food addition and predator reduction in southwestern Yukon to test their effects on hare behaviour and demography. Two areas had food added, one area was fenced to exclude mammalian predators, and one area combined both manipulations. Hares densities were low from 1993 to 1995, and increased after summer 1995. Adult survival was similar throughout. Most deaths were due to predation, despite low densities of predators. Although all treatments had higher hare densities, the manipulations started in the previous increase phase, and densities are probably due to earlier dynamics. Populations increased simultaneously on all sites. Hares on control sites ate more protein and less fibre than did hares elsewhere. These differences resulted from the species and twig sizes they ate. Hares on food addition sites had better overall diets, indicated by lower faecal fibre. On all treatments, hares preferred habitats with little open ground and dense clusters of willow. Hares used the thickest cover when resting, and used more exposed sites while foraging. In summer, they preferred deadfall for immediate cover, but in winter they preferred spruce. Male hares, but not females, had larger home ranges when predators were present. Summer movement rates were also higher on sites with predators. Hares did not respond behaviourally to manipulations of food or predators. Food availability was high and predation risk low: hares may employ many different behavioural strategies with similar demographic impacts. There is no support for a behaviourally-mediated explanation for the demography or duration of the low phase. Adult survival and fecundity did not change, which implies that changes in juvenile survival are crucial to population dynamics. Although behaviour does not appear to affect demography during the low phase, it may do so during the increase and especially the decline phases, when food is more limiting and predation more severe.

Thesis/Dissertation

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2009-06-02

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http://hdl.handle.net/2429/8620

Zoology

University of British Columbia

UBCV

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