STEROID-METABOLISM AND VALIDATION OF NONINVASIVE ENDOCRINE MONITORINGIN THE AFRICAN WILD DOG (LYCAON-PICTUS)

The purpose of this study was to validate noninvasive endocrine monito ring techniques for African wild dogs (Lycaon pictus) and to establish physiological validity of these methods by evaluating longitudinal re productive-endocrine profiles in captive individuals. To determine the primary excretory by-products of ovarian steroid metabolism, [C-14]-p rogesterone and [H-3]-estradiol were co-administered to a female and a ll excreta were collected for 80 hr postinjection. Radiolabel excretio n peaked less than or equal to 18 hr postinfusion, and progesterone an d estradiol metabolites were excreted in almost equivalent proportions in urine (39.7 and 41.1%, respectively) and feces (60.3 and 58.9%, re spectively). Most of the urinary metabolites were conjugated (estradio l, 94.3 +/- 0.3%; progesterone, 90.4 +/- 0.5%), so that immunoassays f or pregnanediol-3 alpha-glucuronide (PdG) and estrogen conjugates (EC) were effective for assessing steroid metabolites. Two immunoreactive estrogens (estradiol and estrone) and at least one immunoreactive prog esterone metabolite (3 alpha-hydroxy-5 alpha, pregnan-20-one) were det ected in feces. Urine and fecal samples were collected (1-3 times per week) for 1.5 yr from one adult female and two adult males to assess l ongitudinal steroid metabolite excretion. Overall correlation of urina ry PdG to matched, same-day fecal progesterone metabolites immunoreact ivity was 0.38 (n = 71, P < 0.05). Similarly, urinary EC was correlate d (P < 0.05) with same-day fecal estrogen immunoreactivity (r = 0.49, n = 71). During pregnancy and nonpregnant cycles, copulation occurred at the time of peak (or declining) estrogen metabolites and increasing progesterone metabolites concentrations. Estrus duration was 6-9 days and gestation lasted 69 days with parturition occurring coincident wi th a drop in progesterone metabolites. Males exhibited seasonal trends in fecal testosterone excretion with maximal concentrations from July to September coincident with peak mating activity. Although these lim ited longitudinal hormone profiles should be interpreted cautiously, n oninvasive gonadal steroid monitoring suggests that: ii) both female a nd male wild dogs may exhibit reproductive seasonality in North Americ a, (7) females are monoestrous, and (3) peak testicular activity occur s between August and October coincident with mating behavior. From a c onversation perspective, noninvasive endocrine monitoring techniques s hould be useful for augmenting captive breeding programs, as well as f or developing an improved understanding of the physiological mechanism s underlying reproductive suppression in response to social and ecolog ical pressures. (C) 1997 Wiley-Liss, Inc.