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The Influence of a Railway on Grizzly Bears (Ursus arctos) in Canada’s Rocky Mountain Parks
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- Author / Creator
- Pollock, Sonya Z
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Linear features such as roads and railways threaten wildlife directly through collisions with vehicles. Although the adverse effects of roads on wildlife have been extensively studied resulting in widespread mitigation measures (e.g. fencing and highway crossing structures), far less attention has been paid to railways. This is unfortunate because railways can have high rates of wildlife-train collisions, which can lessen population viability, particularly for wildlife species that have low reproductive rates, large home ranges, or small and declining populations. This situation has occurred for a population of grizzly bears (Ursus arctos) in Canada’s Rocky Mountain Parks, for which the leading cause of recorded mortality is collisions with trains. To mitigate collision vulnerability for bears in the area one must understand the factors that contribute to bear-train collisions to identify the types of mitigation and locations where it could achieve the greatest benefits.I examined causes of bear vulnerability to railway-associated mortality in three ways. First, I quantified the abundance and phenology of grizzly bear forage plants along the Canadian Pacific Railway in Banff and Yoho National Parks. Second, I investigated the spatiotemporal factors associated with railway selection and movement by grizzly bears using GPS data from 27 collared bears. Further, I determined whether locations of concentrated railway use and movement were correlated with locations of past bear-train strikes. Lastly, I investigated if bears are exposed to toxicants via railway-associated forage (dandelion and train-spilled grain), and if metal concentrations measured in the hair of individual grizzly bears were correlated with their frequency of railway use.I found that the railway had higher species diversity, richness, total cover, and accelerated phenology of vegetation when compared to the adjacent forest. In addition, fruiting species at the railway had higher productivity, earlier ripening, and higher sugar content. Based on information from GPS collars, I found that bears demonstrated strong seasonality in railway use (spring and fall), which may correlate with the seasonal availability of bear-attracting plants that grow along the railway. Bears tended to use the railway in areas with lower landscape-scale habitat quality, where terrain was locally rugged, close to railway sidings (low-speed sections of track), and at intermediate distances from towns, highways, and trails. Among movement types, bears entered the railway where habitat productivity was higher, close to railway sidings, and in locations constrained by local rugged terrain. Bears demonstrated prolonged use of the railway (via continue movements) in areas where landscape-scale terrain was rugged. Step lengths were consistently shorter when bears were on versus off the railway. Locations of concentrated railway use or movement did not predict sites of higher mortality, but prolonged use of the railway (via continue movements) occurred in areas with lower rates of mortality. My analyses of contaminants revealed that railway-associated forage contained elevated levels of 10 heavy metals and 16 PAHs when compared to reference samples, with much higher contamination in train-spilled grain. I found that male bears had higher metal concentrations in hair samples than females, but higher metal concentrations did not correlate with greater frequency of rail use. My results showed that the railway enhances vegetation that may attract bears and other wildlife; that bears use the railway both for foraging opportunities (natural or anthropogenic) and for travel through rugged terrain; and, that railway-associated foods (dandelion and train-spilled grain) contained elevated levels of metals and PAHs. Risk of strike associated with rail use by bears and other wildlife may be reduced by removing attractants, particularly in areas with high rates of past mortality or where rugged terrain constrains movement, and especially in spring and fall. Managers might compensate for attractant removal near the rail by enhancing the productivity of critical bear foods such as berry-producing shrubs, in safe areas via forest thinning or prescribed burns. Removal of attractants, especially grain, and regular maintenance and cleaning of areas of heightened contamination (e g. railway sidings and lubricating stations), may reduce contaminant exposure to wildlife who forage along railways. Wildlife-train collisions will likely increase as railway networks continue to grow. Understanding how railways influence bears and other wildlife, including causes of and mitigation for train strikes, will contribute to the conservation of grizzly bears in North America, and many other sensitive populations worldwide.
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- Graduation date
- Spring 2019
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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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.