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Estimates of the relative effects of demographic parameters on population rates of change, and of the level of natural variation in these parameters, are necessary to address potential effects of perturbations on populations. We used a stochastic model, based on survival and reproduction estimates of the Porcupine Caribou (Rangifer tarandus granti) Herd (PCH), during 1983-89 and 1989-92 to obtain distributions potential population rates of change (r). The distribution of r produced by 1,000 trajectories of our simulation model (1983-89, r = 0.013; 1989-92, r = 0.003) encompassed the rate of increase calculated from an independent series of photo-survey data over the same years (1983-89, r = 0.048; 1989-92, r = −0.035). Changes in adult female survival had the largest effect on r, followed by changes in calf survival. We hypothesized that petroleum development on calving grounds, or changes in calving and post-calving habitats due to global climate change, would affect model input parameters. A decline in annual adult female survival from 0.871 to 0.847, or a decline in annual calf survival from 0.518 to 0.472, would be sufficient to cause a declining population, if all other input estimates remained the same. We then used these lower survival rates, in conjunction with our estimated amount of among-year variation, to determine a range of resulting population trajectories. Stochastic models can be used to better understand dynamics of populations, optimize sampling investment, and evaluate potential effects of various factors on population growth

Harassment of female caribou (Rangifer tarandus) by insects may negatively affect the cows' energy balance during the critical post-calving and lactation period, and certain habitats may provide relief from such harassment. Consequently, we tracked adult, female caribou from the Porcupine Caribou Herd (PCH) by satellite between 25 june and 31 july 1985-89 to determine their habitat preferences during periods of predicted harassment by insects, primarily mosquitoes (Culicidae). When insect harassment was predicted (ambient temperatures ≥13C and winds

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