Comparative analysis of gonadal and adrenal activity in the black and white rhinoceros in North America by noninvasive endocrine monitoring

Abstract

Patterns of fecal reproductive steroid metabolites and adrenal corticoids were characterized for 12-to 24-month periods in black (n = 10 male, 16 female) and white (n = 6 male, 13 female) rhinoceroses at 14 institutions. All black rhinoceros females exhibited at least some ovarian cyclicity on the basis of fecal progestogen analysis (range, 2-12 cycles/yr). However, cycles often were erratic, with many being shorter (<20 days; 18% of cycles) or longer (>32 days; 21%) than the average of 26.8 ± 0.5 days (n = 104 cycles). Five females exhibited periods of acyclicity of 2-10-month duration that were unrelated to season. One complete and seven partial pregnancies were evaluated in the black rhinoceros. Fecal progestogens increased over luteal phase concentrations after 3 months of gestation. Females resumed cyclicity within 3 months postpartum, before calves were weaned (n = 5). Approximately half of white rhinoceros females (6 of 13) showed no evidence of ovarian cyclicity. Of the cycles observed, 5 were "short" (32.8 ± 1.2 days) and 24 were "long" (70.1 ± 1.6 days). Only two females cycled continuously throughout the study. One had both long (n = 9) and short (n = 2) cycles, whereas the other exhibited long cycles only (n = 5). Fecal estrogen excretion was variable, and profiles were not useful for characterizing follicular activity or diagnosing pregnancy in either species. Males of both species showed no evidence of seasonality on the basis of fecal androgen profiles. Androgen metabolite concentrations were higher (P < 0.05) in the black (27.6 ± 6.9 ng/g) than in the white (16.8 ± 3.1 ng/g) rhinoceros. An adrenocorticotropin hormone challenge in four black rhinoceros males demonstrated that the clearance rate of corticoid metabolites into feces was ∼24 hours. Fecal corticoid concentrations did not differ between males and females, but overall means were higher in the black (41.8 ± 3.1 ng/g) than in the white (31.2 ± 1.7 ng/g) rhinoceros. In summary, fecal steroid analysis identified a number of differences in hormonal secretory dynamics between the black and white rhinoceros that may be related to differences in reproductive rates in captivity. Most black rhinoceros females exhibited some cyclic ovarian activity. In contrast, few white rhinoceroses demonstrated evidence of regular estrous cyclicity, and those females that were active had comparatively long cycles. Results also suggest that fecal corticoid concentrations reflect adrenal activity and may be species specific. Continued studies are needed to determine whether fecal corticoid measurements will be useful for understanding the cause of inconsistent gonadal activity in these two species. Because all but three (15.8%) of the white rhinoceroses evaluated in this study were less than 20 years of age compared to 73.1% (19 of 26) of the black rhinoceroses, the impact of age on reproductive and adrenal activity also needs to be evaluated further.

A Validation of Extraction Methods for Noninvasive Sampling of Glucocorticoids in Free‐Living Ground Squirrels

“…These responses are similar to the moderate effects of ACTH reported for some ferrets, rhinoceroses, and chinchillas Young et al 2001;Ponzio et al 2004). As additional studies utilize exogenous glucocorticoid stimulants or suppressors, patterns of differential response as a function of species, population, sex, or individual will become more clear (Hubbs et al 2000;Teskey-Gerstl et al 2000;Brown et al 2001;Goymann et al 2001;Hik et al 2001;Young et al 2001). …”

“…Although the results of study 2 revealed a correlation between basal concentrations of serum corticoids and fecal metabolites, it was necessary to demonstrate a temporal correlation between changes in adrenal activity and changes in glucocorticoid-metabolite levels in feces. In large mammals, an increase in fecal metabolite levels can be detected approximately 24-48 h after an ACTH challenge (Graham and Brown 1996;Monfort et al 1998;Goymann et al 1999;Wasser et al 2000;Brown et al 2001;Millspaugh et al 2002;Wielebnowski et al 2002;Mashburn and Atkinson 2004;Young et al 2004). In smaller mammals (<150 g), fecal glucocorticoid-metabolite levels typically increase within 24 h of stimulation of the adrenal glands or injection of labeled glucocorticoids (e.g., 6-12 h in house mice, deer mice, and red-backed voles [Harper and Austad 2000]; 8-24 h in common marmosets [Bahr et al 2000]; 20-44 h in black-footed ferrets [Young et al 2001]; 30 h in chinchillas [Ponzio et al 2004]).…”

Fecal 20-oxo-pregnane concentrations in free-ranging African elephants (Loxodonta africana) treated with porcine zona pellucida vaccine

“…The remaining values yielded the baseline 5-pregnan-3-ol-20-on concentration. Ovarian cycle length and periodicity was then determined according to the procedure described by Brown et al [45,47]. Phase length estimates as well as ovarian cycle length estimates are given as mean ± SD.…”

“…Individuals were categorized as demonstrating periods of anestrus if they had a follicular phase lasting longer than twice the duration of an average normal follicular phase (≥ 10 weeks) [25,47]. Determination of pregnancy within treated cows was based on luteal phase lengths persisting longer than 3-5 months [21,22].…”

Assessment of Reproductive Function in Southern African Spiny Mice (Acomys spinosissimus) using Faeces as Hormone Matrix

“…Due to the species-specific differences in hormone metabolite excretion (Palme et al 1996;Busso et al 2005) and the presence of different steroid metabolites in the excreta of even closely related species (e.g. Berkeley et al 1997;Schwarzenberger et al 2000;Brown et al 2001), respective assays should be validated in terms of their applicability for the hormone matrix of interest to ensure a reliable quantification of respective hormone metabolites (Hodges et al 2010).…”