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Snowfall, travel speed, and seismic lines: The effects of snow conditions on wolf movement paths in boreal Alberta

  • Author / Creator
    Droghini, Amanda
  • In the winter, snow can present a major challenge to large mammals by impeding locomotion, limiting food availability, and imposing additional energetic costs during travel. This thesis examines the effects of snow conditions on the fine-scale movement patterns of grey wolves (Canis lupus) in a boreal forest ecosystem in northern Alberta. In my first chapter, I use traditional snow tracking to quantify the difference in snow depth and sinking depth between wolf travel paths and measurements 1m and 10m off-path. I compare these results to snow depths recorded at a landscape scale using remote cameras that were deployed across my study area. Wolves’ choice of shallow snow conditions was not consistent across all spatial scales, as snow depth measured by remote cameras was slightly less than the average snow depth 10m off-path. However, at fine spatial scales, snow depth and sinking depth were consistently lowest on wolf travel paths, and highest 10m off-path. The difference in depth that wolves were able to achieve through travel path choices was highly dependent on substrate type. Linear features, and ploughed linear features in particular, were associated with sinking depths and snow depths that were far lower than any other substrate type. Whereas sinking depth for travel paths on natural, uncompacted substrates was 1.1cm less than measurements 1m away, sinking depth for travel paths on ploughed linear features was 4.5cm less than measurements 1m away. Thus, travelling on ploughed linear features may be highly advantageous for wolves, especially as local snow conditions increase. Based on published leg length measurements, we estimated that wolves would start to become impeded by snow conditions when sinking depth reached 18cm (equivalent to 50% sternum height). Over our study, these high sinking depths were encountered 37% of the time. As most of these sinking depths were recorded when wolves were travelling on natural substrates, linear features may provide energetic advantages, especially when wolves are covering large distances or travelling at high speeds. However, although the effects of ploughed linear features may be important in deep snow environments with high levels of industrial or recreational activity, they are unlikely to have an overwhelming impact on locomotion or energetics in the moderate snow conditions that are characteristic of where most wolves in North America are found. In my second chapter, I use remote cameras to identify localized snowfall events, and examine the effects of these events on wolf movements. The effects of snowfall were most noticeable the night of a snowfall event. Relative to my controls, travel speed decreased from 28.1m/min to 20.6m/min the night of a snowfall event. Similarly, the proportion of time spent travelling decreased by 30% compared to controls, from 0.35 to 0.24. The effect of snowfall on movement did not translate into a significant reduction in daily distance travelled; however, relative to controls, wolves travelled nearly 4km less on days of a snowfall event. Because I did not find evidence for persistent effects, I propose that wolves reduce their movements during a snowfall because it is more difficult for them to detect prey, as snowfall can affect wolves’ ability to detect odour trails, in addition to limiting visibility and insulating sound. This thesis furthers our understanding of the grey wolves’ winter ecology in a boreal forest ecosystem that is representative of a large part of their geographic distribution in North America. To my knowledge, this is also the first time that a study has investigated the effects of snowfall events on animal movement in a natural setting. Understanding wolves’ response to snow is important not only for wolf biology, but also for predator-prey interactions. Through their influence on predator movements, snow conditions have the potential to influence encounter rates, predation risk, and kill rates.

  • Subjects / Keywords
  • Graduation date
    2016-06
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/R3CF9JF4J
  • 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
    English
  • Institution
    University of Alberta
  • Degree level
    Master's
  • Department
    • Department of Biological Sciences
  • Specialization
    • Ecology
  • Supervisor / co-supervisor and their department(s)
    • Boutin, Stan (Biological Sciences)
  • Examining committee members and their departments
    • Derocher, Andrew (Biological Sciences)
    • Lewis, Mark (Biological Sciences, Mathematical and Statistical Sciences)