Basal Metabolism and Energetic Cost of Thermoregulation in Wild Turkeys

Abstract

Metabolism of eastern wild turkeys (Meleagris gallopavo silvestris) was measured as a function of temperature during the winters of 1983-84, 1984-85, and the summer of 1984. Basal metabolism (mL oxygen/g/hr) did not differ between sexes within seasons, but was higher for juveniles during winter and adults in summer than for adults in winter. Metabolic costs for thermoregulation below the lower critical temperature (Tc) for females was greater than for males during each season. J. WILDL. MANAGE. 52(1):133-137 Winter starvation is a common cause of mortality in northern populations of the eastern wild turkey. During severe winters mortality is high (540%) in isolated flocks due to restricted energy intake (Austin and DeGraff 1975, Wunz and Hayden 1975, Porter et al. 1983). Calculating daily energy expenditure (DEE) and food intake of wild turkeys under natural winter conditions is important to understand winter survival. Time-energy budget analysis with laboratory derived estimates of metabolic costs is the most popular technique for estimating DEE of freeliving birds (Gessaman 1973, King 1974, Walsberg 1983). Temperature is the most important environmental parameter and the most convenient to control in the laboratory and measure in the field (Kendeigh et al. 1977). Our study measured basal metabolic rate (BMR) and quantified the cost of thermoregulation of captive wild turkeys to establish baseline metabolic data from which DEE models could be constructed. We acknowledge R. W. Hill for use of his laboratory and equipment at Michigan State University. Special thanks go to M. Pollock, D. Dorn, and the crew at the Michigan Department of Natural Resources (MDNR), Mason Wildlife Facility for their maintenance of the captive turkeys used in this study. We thank C. A. Mehl and C. O'Rourke for laboratory assistance, and D. H. Gordon, C. T. Robbins, E. D. Bailey, and an anonymous reviewer for reviewing this manuscript. This study was financed by the MDNR and the Michigan Agricultural Experiment Station. This is Contribution 12146 of the Michigan Agricultural Experiment Station. IPresent Address: Delta Waterfowl and Wetlands Research Station, South Carolina Coastal Waterfowl Project, Star Route 1, Box 226, Georgetown, SC 29440. This content downloaded from 157.55.39.186 on Tue, 12 Apr 2016 10:34:39 UTC All use subject to http://about.jstor.org/terms 134 COST OF THERMOREGULATION IN TURKEYS * Gray and Prince J. Wildl. Manage. 52(1):1988 Table 1. Sex, age, source, and number of captive turkeys used in metabolic experiments during each season. Source Test Season Sex Age period Wild Pilarski Total Winter F Juv 16 Feb-18 Mar 1984 2 5 7 Ad 29 Dec-20 Mar 1985 4 5 9 M Juv 29 Dec-20 Mar 1985 6a Ad 29 Dec-20 Mar 1985 1 5 6 Summer F Ad 5 Jul-10 Sep 1984 4 5 9 M Ad 5 Jul-10 Sep 1984 1 5 6 a Birds were progeny of Pilarski males x wild females raised in captivity.