Michael E. Lisano

Seasonal Variations in Plasma Testosterone Level in Male Eastern Wild Turkeys

Testosterone level was determined, by radioimmunoassay, on 137 plasma samples obtained from male eastern wild turkeys (Meleagris gallopavo) over a 15-month period, in Alabama. Ninety-three samples were obtained from 3 pen-reared birds by making collections every 2 weeks for 62 consecutive weeks; 14 samples were from trapped birds; and 30 were from gobblers killed during the regular spring hunting season. Plasma testosterone levels for pen-reared birds at 6 weeks of age (July 1974) were 3263 ng/100 ml; whereas those at 34 weeks of age (January 1975) and just prior to breeding season were 87-108 ng/100 ml. Mean plasma testosterone level in January-February for the mostly adult trapped birds was 202.2 ? 61.9 ng/100 ml compared to 146.0 ? 62.3 ng/100 ml for the subadult pen-reared birds. Values for the mostly adult gobblers killed during the March-April hunting season was 344.9 -+110.8 ng/100 ml compared to 254.4 _ 140.5 ng/100 ml for the subadult pen-reared turkeys. Changes in behavior and body conformation in relation to changes in plasma testosterone level are discussed for the three pen-reared turkeys. J. WILDL. MANAGE. 41(2):784-188 Knowledge of the seasonal variations in sex hormone level in male eastern wild turkeys is important for a more precise delineation of the birds breeding season, and also for a better understanding of its behavioral and anatomical changes. This information can be useful to game managers as an additional tool for evaluating reproductive status in wild populations. Information regarding the seasonal variations in plasma testosterone levels in either wild or domestic turkeys is lacking. Furthermore, no specific value for plasma testosterone level has been reported for males of either wild or domestic turkeys. In a brief abstract, Zimmerman and Wentworth (1974) reported that they had measured the serum testosterone level in large white domestic turkeys in response to changes in photoperiod; however, they gave no specific data. Arcos (1975) reported the isolation of testosterone from the ovarian blood of the laying turkey but did not quantify the level. Plasma testosterone level for the male domestic fowl has been reported as 84-783 ng/100 ml (Furr and Thomas 1970) and for the mallard (Anas platyrhynchos) as 65-270 ng/100 ml by Jallageas and Attal (1968, cited by Bell and Freeman 1971). Changes in the circulating level of the androgens, and more specifically testostero e, are responsible for changes in male secondary sex characteristics in most vertebrates. These may include cyclic or acyclic changes in body color, body conformation, vocalization, breeding condition and sexual b havior (Turner and Bagnara 1971). Male eastern wild turkeys exhibit both behavioral and anatomical changes during their breeding season. Birds become belligerent toward other males, and courtship display toward females becomes active. Seasonal changes in body conformation include increased brilliance of facial color in caruncles and throat wattle, and the development of a large fatty breast sponge. All of these changes presumably are related to changes in the circulating levels of androgens, particularly testosterone. We wish to thank W. H. Hamrick, Wildlife Biologist, Alabama Department of Conservation, and J. R. Gwaltney, research 184 J. Wildl. Manage. 41(2):1977 This content downloaded from 157.55.39.243 on Thu, 06 Oct 2016 04:56:19 UTC All use subject to http://about.jstor.org/terms SEASONAL VARIATIONS IN WILD TURKEY TESTOSTERONE ? Lisano and Kennamer 185 assistant, Auburn University, for their assistance in obtaining blood samples. We are also grateful for the technical assistance of H. E. Whatley, graduate assistant, Auburn University, in the determination of plasma testosterone levels. MATERIALS AND METHODS

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

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 Williamss 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

Variations in Plasma Thyroxine (T 4 ) and Triiodothyronine (T 3 ) in Eastern Wild Turkeys

A total of 185 plasma samples, from 3 different groups of eastern wild turkeys (Meleagris gallopavo silvestris), were analyzed for thyroxine (T4) and triiodothyronine (T3) by radioimmunoassay. Of this total, 118 were from 4 pen-reared birds sampled biweekly for 14 months, 43 were from trapped birds, and 25 were from gobblers killed during the spring hunting season. Variations in plasma T, level corresponded to changes in environmental temperature and to the molting process. However, variations in the plasma T3 level of the pen-reared birds could not be correlated with seasonal changes. Total plasma thyroid hormones (T4 + T3) varied in the same manner as T4 alone. There were significant differences (P 0.05) due to sex or age were found in plasma T1, T, or T, + T3. J. WILDL. MANAGE. 41(4):650-656 Thyroid hormone deficiency (hypothyroidism), such as that produced by iodine deficiency, thyroidectomy, or feeding or of an antithyroid agent, has been shown to decrease egg production in domestic chickens (Winchester 1939) and to cause cessation of spermatogenesis in roosters (Maqsood 1952). Growth and development are also retarded by hypothyroidism (Winchester and Davis 1952, Singh et al. 1968). A decrease in thyroid function in free ranging populations of eastern wild turkeys might affect their reproductive performance, and thus, result in a decrease in the actual number of turkeys in that population. This study presents the possibility of using plasma levels of thyroid hormones as an indicator of the physiological status of eastern wild turkey populations. Before investigations can be undertaken to determine the existence of thyroid hormone deficiency on populations of free ranging wild turkeys, the following questions need to be answered: (1) What are the ranges for normal plasma levels of thyroid hormones? (2) Do the levels of these hormones exhibit variations due to sex, age, and seasonal changes? (3) Do values differ between samples obtained from pen-reared, trapped, and killed wild turkeys? (4) Since there are 2 principal thyroid hormones, triiodothyronine (T3) and thyroxine (T4), should both or only 1 be measured? The authors wish to thank W. H. Hamrick, Wildlife Biologist, Game and Fish Division, Alabama Department of Conservation, and J. R. Gwaltney, research assistant, Auburn University, for their assistance in obtaining blood samples from trapped and killed specimens. This research was supported in part by funds from a special appropriation from the Alabama State Legislature to the Alabama Cooperative Wildlife Research Unit. MATERIALS AND METHODS

Plasma Estrogens, Total Protein, and Cholesterol in the Female Eastern Wild Turkey

Changes in blood chemistry can be used to monitor the reproductive status of free-ranging female eastern wild turkeys (Meleagris gallopavo silvestris). The objectives of this study were to evaluate seasonal changes in several blood parameters in relation to changes in breeding condition. Estrogens were measured from blood samples taken biweekly before, during, and following the breeding season. Total plasma protein and plasma cholesterol were also quantified.

An isotope‐powered thermal storage unit for space applications

An Isotope‐Powered Thermal Storage Unite (ITSU), that would store and utilize heat energy in a ‘‘pulsed’’ fashion in space operations, is described. Properties of various radioisotopes are considered in conjunction with characteristics of thermal energy storage materials, to evaluate possible implementation of such a device. The utility of the unit is dicussed in light of various space applications, including rocket propulsion, power generation, and spacecraft thermal magnagement.

Effects of Alpha-Chloralose Drugging on Blood Constituents in the Eastern Wild Turkey

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