Herbivory interactions between beaver (Castor canadensis ) and elk (Cervus elaphus) on willow (Salix spp.) in Banff National Park, Alberta

I examined the herbivory interactions between beavers ( Castor canadensis), elk (Cervus elaphus), and willow (Salix spp.) in the Bow Valley in Banff National Park, Alberta. I found that beavers foraged selectively on willow, selecting larger than average stems of tall (≥250 cm) willow. The amount of willow food biomass within 30 m of the shoreline of the Vermilion Lakes Wetland (VLW) is substantially lower than what was present near active beaver lodges in other areas, suggesting that there is insufficient food in the VLW for beavers at present time.;The combined effects of beaver cutting followed by elk browsing eliminated tall willow communities in the Vermilion Lakes Wetland. Willows that had been cut by beavers and browsed by high densities of elk were in shorter height classes (<100 cm), than willow communities affected by either beaver or elk alone. These beaver-elk interactions may be an example of exploitative competition, where elk have excluded beaver from the Vermilion Lakes Wetland by browsing on willow.;I compared two areas of the Bow Valley, the central zone and the western zone. The central zone is characterized by high elk densities, few beaver, few wolves, heavy human presence, short heavily browsed willow, and low songbird diversity and abundance, while the western zone is characterized by low elk densities, beaver with adequate food resources, wolves, lower human presence, tall lightly browsed willow, and higher songbird diversity and abundance. These interactions were consistent with a top-down (predator driven), trophic cascade ecosystem, where the presence or absence of large predators, in this case wolves, has had a dramatic effect on lower trophic levels.