Complexity of food web interactions in a large mammal system

• Main Author: Eisenberg, Cristina
• Other Authors: Hibbs, David E., Doescher, Paul S., Sanchez, Dana, Vavra, Martin, Salwasser, Hal, Moldenke, Andrew, Forest Engineering Resources and Management, Oregon State University. Graduate School
• Format: Doctoral or Postdoctoral Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: Elk > Behavior > Waterton-Glacier International Peace Park (Mont. and Alta.); Gray wolf > Effect of fires on > Waterton-Glacier International Peace Park (Mont. and Alta.); Populus tremuloides > Effect of fires on > Waterton-Glacier International Peace Park (Mont. and Alta.); Elk > Ecology > Waterton-Glacier International Peace Park (Mont. and Alta.); Food chains (Ecology) > Waterton-Glacier International Peace Park (Mont. and Alta.); Elk > Effect of fires on > Waterton-Glacier International Peace Park (Mont. and Alta.); Elk > Predators of > Ecology > Waterton-Glacier International Peace Park (Mont. and Alta.); Gray wolf > Ecology > Waterton-Glacier International Peace Park (Mont. and Alta.); Elk > Effect of predation on > Waterton-Glacier International Peace Park (Mont. and Alta.); Populus tremuloides > Ecology > Waterton-Glacier International Peace Park (Mont. and Alta.); Alta; Canada; North Fork; Canis lupus; gray wolf
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/bk128d43j

Food webs consist of a combination of bottom-up (resource-driven) and top-down (predator-driven) effects. The strength of these effects depends on the context in which they occur. I investigated food web (trophic) relationships between wolf (Canis lupus) predation, elk (Cervus elaphus) herbivory, aspen (Populus tremuloides Michaux) recruitment, and fire. The study setting, in the central portion of the Crown of the Continent Ecosystem, spans the US/Canada border and encompasses Glacier National Park (GNP), Montana and Waterton Lakes National Park (WLNP), Alberta. I stratified my observations across three spatially distinct areas, the North Fork Valley, in the western portion of GNP; the Waterton Valley, in the eastern portion of WLNP; and the Saint Mary Valley, in the eastern portion of GNP. All valleys are elk winter range (low-lying grasslands with patches of aspen). The valleys have three different observed wolf population levels (Saint Mary: low; Waterton: moderate; North Fork: high), which represent three levels of long-term predation risk (the probability of an elk encountering a wolf). Ecological characteristics (e.g., climate, soils, elevation, plant associations) are comparable among valleys. Fire has occurred in 90% of the North Fork. My objective was to examine the relative influence of bottom-up (fire) and top-down (predation risk) factors and the context-dependence of these relationships via data gathered during a three-year time span. I found complex elk responses to bottom-up and top-down factors that could influence habitat use by elk. Pellet transect data demonstrated that elk exhibited the same risk reduction behavior at all wolf population levels, even at very low levels. Predation risk variables that provided impediments to detecting or escaping wolves had a similar and negative influence on occurrence of elk (pellet piles), regardless of wolf population density. Fire had a negative effect on elk density and a positive effect on wolf density (per scat piles) in aspen communities where a high ...