Cardiac and Behavioral Responses of Mountain Sheep to Human Disturbance

Abstract

Telemetered heart rates (HR) and behavioral responses of mountain sheep (Ovis canadensis canadensis) reacting to human disturbance in the Sheep River Wildlife Sanctuary, southwestern Alberta, were recorded. Cardiac and behavioral responses of sheep (4 ewes, 1 ram) to an approaching human were greatest when the person was accompanied by a dog or approached sheep from over a ridge. Reactions to road traffic were minimal as only 8.8% of vehicle passes elicited HR responses. No reactions to helicopters or fixed-wing aircraft were observed at distances exceeding 400 m from sheep. Responses to disturbance were detected using HR telemetry that were not evident from behavioral cues alone. However, mean duration of the HR response (138.6 sec) was not greater (P > 0.05) than mean period of the behavioral reaction when sheep were alert or withdrawing from harassing stimuli (112.4 sec). Use of HR telemetry in harassment research is discussed. J. WILDL. MANAGE. 46(2):351-358 Survival and optimal use of habitat by individuals demand high levels of vigilance so that stimuli indicating presence of predators, conspecifics, food, or shelter do not go undetected (Dimond and Lazarus 1974). Yet if an animal is excessively aroused, as from human disturbance, the added cost of excitement may interfere with health, growth, and reproductive fitness (Geist 1979:5). Recent studies of free-living birds (Kanwisher et al. 1978) and ungulates (Ward et al. 1976, MacArthur et al. 1979) have revealed that heart rate is a sensitive indicator of arousal, the first stage of an alarm reaction to stress (Jenkins and Kruger 1975). These and other investigations (Thompson et al. 1968, Cherkovich and Tatoyan 1973, Moen et al. 1978) have demonstrated consistent HR responses to disturbing visual or auditory stimuli, often in the absence of overt behavioral changes. Expanding upon earlier work (MacArthur et al. 1979), the present paper integrates cardiac and behavioral observations to better understand how individuals in a population of mountain sheep perceive and respond to environmental perturbations. In view of escalating use of alpine areas by hikers, particular attention is focused on the sensitivity of sheep to approaches by humans (Dunaway 1971). The study also addresses relative merits of HR telemetry and overt behavioral observations as methods for detecting and defining harassment responses in ungulates. Preliminary findings (MacArthur et al. 1979) suggested cardiac responses may persist longer than behavioral reactions, and a quantitative comparison of these 2 indices of disturbance is reported here. We acknowledge the field assistance of D. MacArthur, B. Horejsi, G. Lynch, J. Jorgenson, D. Olsen, and D. Nugent. We thank the technical staff of the Department of Electrical Engineering, University of Calgary, for constructing transmitters and other electronic equipment essential to this study. Cooperation provided by the Alberta Forest Service and Alberta Fish and Wildlife Division is also appreciated. Financial support was proIPresent address: Department of Zoology, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada. J. Wildl. Manage. 46(2):1982 351 This content downloaded from 157.55.39.180 on Mon, 25 Apr 2016 06:15:48 UTC All use subject to http://about.jstor.org/terms 352 RESPONSES OF MOUNTAIN SHEEP TO DISTURBANCE* MacArthur et al. vided by the Natural Sciences and Engineering Research Council of Canada, and by the Foundation for North American Wild Sheep.