The ecological role of elk in Rocky Mountain National Park

Monello, Ryan; Johnson, Therese; Wright, R

There is little evidence that elk herbivory is negatively affecting white-tailed ptarmigan in alpine tundra areas. However, several factors strongly suggest more research is needed before the effects of elk can be discounted, including the negative correlation between elk and ptarmigan numbers, high percentage of alpine willow in elk summer diets, and possible declines in alpine willow coverages. Increased winter temperatures have also been suggested to negatively affect ptarmigan population growth rates and must also be considered in any future research. Bird and butterfly diversity has been found to be highest in aspen, willow riparian, and ponderosa pine habitat on the primary winter range. No studies have shown a direct effect of elk on these animal species in RMNP, but the large impact of elk on these habitats on the core winter range, which contains the majority of these habitats, should be a management concern. In particular, these habitats support a distinct biological community at these elevations that are not found elsewhere in the park because almost all other aspen and willow stands are located at higher elevations in either coniferous forests or alpine tundra. The mechanism by which elk are suggested to decrease bird abundance is via decreased live trees in aspen stands and decreased structural complexity of shrubs in aspen and willow habitat. If current trends continue it could lead to the local exclusion of several cavity nesting and willow-dependent bird species. Beaver declines in RMNP are believed to initially be due to trapping that began in the 1940s. Beaver declines over the last 50-60 years contributed to a loss of water and willow on the core winter range. Subsequent declines or lack-of-recovery of beaver is attributed to competition with elk for food, in particular tall willow, which has a limited distribution on the core winter range. As remaining tall willow on the core winter range are cut for food by beaver, their subsequent regrowth is suppressed by elk. This is leading to further declines in the beaver and willow populations.

The ecological role of elk in Rocky Mountain National Park

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