Plasma Corticosterone Level as an Indicator of Stress in the Eastern Wild Turkey

Abstract

Plasma corticosterone levels were measured in three groups of eastern wild turkeys (Meleagris gallopavo) by a competitive protein binding technique. Three male and 1 female turkeys were pen-reared and sampled bi-weekly for 54 weeks, resulting in 112 samples. Ten male and 22 female birds were trapped and comprised the second group, while the third group consisted of 20 male birds killed during the spring hunting season. There were no significant differences (P > 0.05) between the plasma corticosterone levels of pen-reared (2:13 -+ 0.11 /jg corticosterone/dl plasma) and killed males (1.96 ? 0.13 /4g/dl). Other average values were: (a) pen-reared female (2.09 ? 0.15 /tg/dl); (b) trapped males (6.28 ? 0.78 /xg/dl); and (c) trapped females (5.71 ?_ 0.99 ,tg/dl). In all cases trapped birds had a significantly higher (P < 0.05) corticosterone level than did pen-reared and killed birds. No significant differences between adults and juveniles were apparent. J. WILDL. MANAGE. 41(2):189-193 Management of eastern wild turkeys and their habitat would be enhanced by the availability of one or more indices by which the level of stress to which the birds are subjected could be quantitated. For example, such indices should enable game managers to determine more readily the condition of their wild turkey populations relative to optimum conditions for these birds. There is no literature available on the level of plasma corticosterone in the wild turkey. Changes in the level of plasma glucocorticoids are commonly used as a measure of stress in many species of animals. Brown (1961) showed that the major glucocorticoid secreted by the avian adrenal gland is corticosterone. Also, changes in the corticosterone level in the peripheral blood of the domestic turkey reflect the severity of the stress. Nagra et al. (1958), using a fluorometric procedure, measured the level of corticosterone in 6-month-old male broadbreasted bronze turkeys under NembutalTM anesthesia and found a level of 7.0t 0.4 jig corticosterone/dl plasma. In the adrenal effluent blood of the same animals they found a level of 42.4 5.3 C/g/dl. Brown (1961) reported normal peripheral values in 6-week-old domestic turkey poults to be slightly higher. Using a fluorometric assay, he found a range of values from 11.3 to 12.5 /g/dl. Bajpayee and Brown (1972) reported a lower level of corticosterone in the plasma than any other workers. In female Williams's bronze domestic turkeys they found a range of values from 1.52 to 2.78 pg/dl using a fluorometric assay. The authors wish to thank W. H. Hamrick, Alabama Department of Conservation, and J. R. Gwaltney, Auburn University, for their assistance in obtaining blood samples. MATERIALS AND METHODS