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Examining predation risk and antipredator responses of snowshoe hares in Northern Canada’s boreal forest
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- Author / Creator
- Shiratsuru, Shotaro
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Predators limit prey populations not only through direct killing of prey but also through changes in behavior due to predation risk and negative fitness consequences that result. Prey species are known to respond to both predictable (e.g. risky times and places) and unpredictable variation (e.g. predator encounters) in predation risk by adopting proactive and reactive antipredator responses respectively, but proactive and reactive antipredator responses have been rarely examined simultaneously in a single study. Snowshoe hares (Lepus americanus) which are known for their 10-year population cycle are the major prey for multiple predator species and thus a keystone herbivore in North America’s boreal forest. The hare population cycle is known to be driven by predators directly through predation but may also be potentially influenced by non-consumptive effects of predators such as physiological stress negatively affecting body condition and reproduction of hares. In this thesis, I (1) investigate a reactive antipredator response (reduction in foraging) of hares to unpredictable (acute) predation risk and (2) identify temporal patterns of hare predation and behavioral patterns of hares before predation, aiming to contribute to a more comprehensive understanding of predation risk and antipredator responses.
In chapter 1, I examined the effects of food availability and long-term predation risk, by manipulating food availability for hares via individual-based food supplementation and by monitoring two-month mortality rate of hares. I found that hares reduced foraging time as a reactive antipredator response after lynx encounters and the magnitude of the response was affected by the interaction between food availability and long-term predation risk. In chapter 2, I examined risky time and behavior for hares. Daytime and bright moonlit nights could be the riskiest time for hares, but hares were killed frequently both during the daytime and the night/dawn/dusk, possibly because different predator species preyed upon hares at different times of day; lynx and great horned owl predation occurred almost equally during the day and the night/dawn/dusk, and coyote and goshawk predation occurred mostly during the daytime. Hares did not show higher foraging rate before predation than their average foraging rate, and this finding imply that hares are exposed to high risk of predation regardless of whether they are foraging or not. Considering that hares spend most of their time and are killed by predators mostly in a spruce forest and that hare habitat is relatively homogeneous in Northern Canada’s boreal forest, spatiotemporal refugia may not be common for hares. Overall, my research revealed that hares are experiencing both predictable and unpredictable variation in predation risk, and are potentially responding to both types of variation in predation risk simultaneously by adopting proactive and reactive antipredator response respectively. I suggest that future studies should both proactive and reactive antipredator responses simultaneously, to better understand non-consumptive effects of predators on prey populations. -
- Graduation date
- Fall 2020
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.