Pictures of wildlife taken in southwestern Alberta using infrared camera traps.
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PhD thesis abstract:: Humans influence the density and distribution of other species through direct and indirect effects. Effects are indirect when a species influences another species via an intermediate species, whereas direct effects have no mediator. Humans have strong negative direct effects on wolves (Canis lupus) in areas where wolves kill livestock. Such effects could indirectly influence other species in food webs, particularly wolf prey (i.e., herbivores such as elk; Cervus elaphus) and vegetation species eaten by herbivores. In addition, humans simultaneously directly influence several species in food webs, triggering numerous indirect effects. For example, humans have direct effects on forage (e.g., through agriculture) that could indirectly influence herbivores (e.g. by providing food).
I studied direct and indirect effects of humans on several interacting species in a terrestrial food web. First, I found that despite the minor cost of livestock predation when evaluated in the broader context of the rural economy, it still constitutes an important issue that compensation programs will not easily eliminate. Livestock predation will likely continue to elicit strong direct effects of humans on wolves. Second, I found direct effects of wolves on prey. Elk selected forest cover and low-food-quality habitat in response to wolf presence. Cattle (Bos taurus) selected roads (likely to seek human protection) and low-food-quality habitat, but only after wolves left pastures, indicating poor anti-predator behaviour. Despite presence of the top-down effects described above, path analysis indicated that humans influenced species distribution from the bottom-up with direct effects on forage and positive indirect effects on herbivores (elk and cattle) and wolves. As a result, human presence influences multi-species assemblages. An overall assessment of mammalian species (humans included) relative density in the study area demonstrated that large herbivores were three times more abundant on high-use roads and trails whereas predators were less abundant.
I documented strong direct and indirect effects of humans on an entire food web. To fully understand and where necessary mitigate the impact of humans on species in an ecosystem, managers must not limit their considerations to direct effects, but also consider the indirect effects on species at several trophic levels of food webs.
Photo of the researcher measuring herbivory in the Carbondale River area of southwestern Alberta.
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In this project, Marco supervised 3 students: one PhD, Muhly and two Masters, all funded by NSERC scholarships. Dr. Musiani also supervised one post-doc involved in the project, Dr. McDevitt. Their exciting findings are explained under the student sections. Marco has contributed to all aspects of research design and delivery for the project, including elk and human-use data collection and analyses. He regularly meets with researchers and other collaborators to discuss research plans, design and direction. He has also participated in community outreach open houses in the study area.
In 2009 and 2010, Marco also published two ëwolf-centred’ books with contributions form International authors (see figures). These books also highlight wolf behaviour and the problems caused by wolves in SW Alberta. For centuries wolves have been the subject of fairy tales and folklore, embodying mystery, cunning, and threat. Now as wolves make a come-back, their proximity continues to captivate or incite debate. Therefore, these books must deal with wolf behaviour, biology, habitat, and most particularly the relationship between wolves and people.
The goal of my portion of the project is to provide a better understanding of how roads, human activity on these roads, and access management influence elk ecology. We will implement a before-after-control-impact (BACI) design to experimentally manipulate human access on the landscape to determine its effectiveness at enhancing elk habitat, movement, and ultimately demographics. We will do this by examining three aspects of elk life history: habitat selection, movement, and survival. Further, we propose to use models of elk habitat selection, movement and survival to project how implementation of access management could influence population demographics and change the amount of ‘usable’ or ‘effective’ habitat available. Our specific objectives are to:
- Build seasonal resource selection functions to characterize patterns of elk use of the landscape and to determine how roads and access management influence these models. We will map the distribution of elk habitats under a variety of land-management and access-management strategies.
- Build movement models using step selection functions and autoregressive techniques to assess how roads, human-use of roads, and industrial activity influence elk movements. We will use access management manipulations to differentiate between the effects of a linear feature on the landscape and the combination of roads with human activity.
- Generate and parameterize a biologically meaningful survival model for elk that will incorporate landscape variables and then model the potential effects of various access management regimes on population dynamics and growth.