Responses of Bull Elk to Simulated Elk Vocalizations during Rut

We studied the responses of mature, bull elk (Cervus elaphus nelsoni) to repeated bugling that simulated a technique used by hunters to harvest elk. Our study was conducted on the Forbes Trinchera Ranch in southcentral Colorado during September and October 1988-89. We repeatedly approached and bugled at individually radio-collared bulls. To instill negative reinforcement, treatment bulls were harassed by the sound of a shot after bugling sessions; control bulls were not. We used a logistic regression model to test the bulls' ability to learn to avoid hunter vocalizations after repeated harassment. A model that fit the observed data included previous harassment (P = 0.030, 1988; P < 0.0001, 1989), suggesting that repeatedly harassed bulls can learn to avoid a bugling hunter. J. WILDL. MANAGE. 55(3):396-400 Several hypotheses regarding the function of bugling by bull elk have been suggested. Bulls may bugle to advertise to cows (Struhsaker 1967, Geist 1982), to bring harem members closer together (Bowyer and Kitchen 1987), or to assess the fighting ability of other bulls (Clutton-Brock and Albon 1979). During rut some bulls will respond to bugling by searching out and chasing off intruders (Geist 1982, Bowyer and Kitchen 1987); others will try to threaten the intruder with bugles of their own (Harper et al. 1967, Lincoln et al. 1970, Clutton-Brock and Albon 1979). These responses are regularly exploited by hunters during rut. Because the number and proficiency of hunters attempting to harvest bull elk during rut has increased, wildlife managers are concerned that this technique could result in an overharvest or excessive disturbance of bulls during a time of year when they are highly vulnerable. Shooting in the immediate proximity of an elk may cause it to run several kilometers (Skovlin 1982) or to move off into distant, heavily-timbered areas (Ward 1973, Wright 1983). Batcheler (1968) thought that persistent hunting in New Zealand caused a shift in habitat use and an increase in nocturnal activity. If bulls did not develop an avoidance response to hunter bugling, concern about further behavioral and physiological effects of heavy hunting pressure during the rut might be warranted. Artificial bugling by hunters represents a unique type of disturbance, the effects of which have not been determined. Our objective was to determine whether individual bulls learn to cease responding when they are repeatedly harassed after approaching a simulated bugle. We administered the aversive stimulus of firing a blank from a revolver to treatment bulls to experimentally test bull