The National Park Service defines a non-native species as one that occurs as a result of direct or indirect, deliberate, or accidental actions by humans. This definition recognizes that parks are places intended to preserve natural, ecologically balanced communities. Often non-natives disrupt this balance.
Mountain goats, introduced by the state of Colorado's Division of Wildlife to the Mount Evans area, occasionally make their way north to the park. Because these animals carry diseases that can infect bighorn sheep, and also compete with the native sheep for food, the park has taken active measures to remove goats that enter the park. Usually the goats are captured and taken back to Mount Evans. However, park policy permits shooting of goats if they cannot be trapped.
Non-native plant species may dramatically change a visual landscape by completely dominating an area that once held a mix of native species. Leafy spurge, a plant that has been found in Rocky Mountain National Park, is an example of a species that has had this type of impact where it has been left uncontrolled. Another non-native plant of concern, common burdock, has been documented to fatally trap hummingbirds with its sticky sap.
In 2002, about 80 acres of the park were treated for non-native plant infestations. Treatment methods included hand-pulling, cutting, chopping, scalding, and using insect controls. At the present time, the park is not using any herbicides to control these species.