Heart rate responses of bighorn sheep to environmental factors and harassment
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AbstractThe responses of five free-ranging bighorn sheep to their environment were evaluated via heart rate telemetry, on Ram Mountain, Alberta, from June to August, 1979. Heart rate is a well-established correlate of anxiety and arousal, i.e. a good indicator of stress. The effects of environmental factors on heart rate were examined by multivariate analysis. Results were adjusted for interactions among the factors and for the effects of activity, metabolic weight, individual differences, and for time of day, since the sheep displayed circadian heart rate rhythms. Thermal conditons were evaluated using a black - bulb thermometer. Higher heart rates occurred both belCM and above the thermoneutral zone, indicating cooling and heat stress, respectively. Certain habitat features were important to the security of the sheep: heart rate increased exponentially with distance from cliffs, and was higher when the sheep were in unsecure habitat (meadows and shrubbery), when low on slopes, or when near a road. Good visibility and advantageous footing appeared to reduce anxiety. Responses to tree cover were ambivalent, showing it provided security under certain conditions. Security needs limited habitat use by the sheep. The effects of intruders were evaluated by the length of time over which they caused significantly higher heart rates in the sheep. This showed intruders could cause considerable stress. Withdrawal occurred in 60% of all approaches. Behaviour was, however, a poor indicator of the stress response to intruders. Strategies are recommended for the management of bighorns, notably preservation of habitat that meets both their security and physical needs, and control of human access to sheep range.
Bibliography: p. 285-314.
CitationStemp, R. E. (1983). Heart rate responses of bighorn sheep to environmental factors and harassment (Unpublished master's thesis). University of Calgary, Calgary, AB. doi:10.11575/PRISM/20541
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