Elk (Cervus canadensis) are native to the park. Predation by wolves historically limited the density of elk and kept the animals moving, but wolves (Canis lupus) were

hunted to extinction in Colorado by about 1940 ( Armstrong, 1972). Elk were hunted to extinction in the vicinity of what later became Rocky Mountain National Park by 1900, but 49 elk were transplanted from the Yellowstone herd in Wyoming during 1913–14 ( Hess, 1993). The elk population reached 350 by 1933, when the population was judged to have met or exceeded the carrying capacity of the park’s lower elevation valleys that provide elk winter range ( Hess, 1993). Although elk hunting is permitted in the surrounding national forests, hunting is not permitted within the national park and elk have learned to remain within the park boundaries. Elk numbers increased

Akt inhibitor dramatically during the period 1933–1943, decreased in response to controlled shooting during 1944–1961, and subsequently rose rapidly to 3500 by 1997 ( Hess, 1993 and Mitchell et al., 1999). Like many grazing Panobinostat chemical structure animals, elk prefer to remain in riparian zones, and matched photos indicate substantial declines in riparian willow and aspen during periods when elk populations increased. Although other factors may have contributed to the recent decline in beaver numbers, increased riparian grazing by elk likely influences beaver food supply and population. Beaver reintroduction in connection with riparian restoration requires, first, that beaver have an adequate supply of woody riparian vegetation for food and for building dams. About 200 aspen trees are needed by isothipendyl each beaver each year (DeByle, 1985). Second, reintroduction requires that the region includes sufficient suitable habitat to permit dispersal and genetic exchange between colonies of beavers on a river and between rivers. Beaver colony size can vary widely, but averages 5–6 animals. Each colony has a minimum territory of 1 km along a stream (Olson and Hubert, 1994). Third,

successful reintroduction requires that human communities sharing the landscape accept the presence of beaver. Although the latter point might not seem as important in a national park, beaver continue to be removed in many regions because of perceived negative consequences of their presence, including water impoundments and overbank flooding, felling of riparian trees, and pulses of coarse wood to downstream river segments if beaver dams fail during peak flows. Options for riparian restoration in Rocky Mountain National Park include gradual and more abrupt measures. Gradual measures include grazing exclosures that include some lag time for woody riparian vegetation to regrow, self-reintroduction of beaver from populations outside the park boundaries, and measures to limit elk populations to 600–800 animals within the park.