National Park Service


Date of this Version



Prepared for the 36th North American Wildlife and Natural Resources Conference

Portland, Oregon, March 7-10, 1971.


The results from studies of both naturally and artificially regulated ungulate populations in four Rocky Mountain parks are reviewed. Study findings on population regulation processes, the role of predators, natural mortality and natality, and ungulate habitat and food relationships suggest that previous assumptions which were the basis for artificially regulating ungulates over-estimated the regulatory effects of predators and did not always distinguish natural from human-influenced conditions or changes. The suggested rationale for artificially regulating native ungulates in Rocky Mountain parks is: a human influence that causes unnatural successional trends by restricting ungulates from freeranging over an ecologically complete habitat (1) cannot be removed, (2) can be rectified by artificially regulating ungulate numbers, and (3) that such regulation will not cause greater departures from natural relationships in a biological system than accepting a new equilibrium. The rationale for relying on natural regulation processes in parks is that ungulates are not causing unnatural successional trends, or the antithesis of the rationale for artificial regulation. Fundamental considerations for applying the rationale are presented.