ELK BEHAVIOR IN RESPONSE TO HUMAN DISTURBANCE AT MOUNT ST HELENS NATIONAL VOLCANIC MONUMENT

The edge of the Mount St. Helens volcanic blast zone attracts high summer densities of Roosevelt elk (Cervus elaphus roosevelti). Forest Service Road 2560 (a previously existing logging road) was opened to the public in the Clearwater drainage of the blast zone in 1987, and elk use was monitored. During that year, elk avoided a 500 m corridor centered on the road, as well as several sections in the study area where the influence of the road was prominent. This avoidance was probably a learned behavioral response to public use of Forest Service Road 2560 but might also reflect a higher frequency of flight reactions to traffic. Maximum herd size also decreased in 1987 as a response to frequent passive harassment by humans on Forest Service Road 2560 (such as getting out of cars), as large herds were more likely to be seen and were more vulnerable to initiation of a flight reaction. Logging also produced by-products of human activity that constituted passive harassment even when humans were temporarily absent (e.g. foreign noises and materials). Elk tolerance of timber operations was correlated positively with proximity to hiding cover. A high level of habituation by elk to disturbance in the Clearwater blast zone will probably be preceded by the hiding cover stage of plant succession.