Measuring Faecal Epi-Androsterone as an Indicator of Gonadal Activity in Spotted Hyenas (Crocuta crocuta)

Abstract

Enzyme immunoassays (EIA) that measure faecal testosterone metabolites (fTM) are useful tools to monitor gonadal activity. The aim of this study was to validate an “in-house” epiandrosterone EIA to monitor fTM in spotted hyenas. FTM were characterised in a male and a female hyena that each received an injection of 3H-testosterone. High-performance liquid chromatography (HPLC) analyses revealed a cluster of highly polar enzyme-hydrolysable hormone metabolite conjugates. We performed hydrolysis using β-glucuronidase to deconjugate metabolites and improve sensitivity of the assay. Because β-glucuronidase from Helix pomatia has been reported to bias testosterone measurements in some species, we compared the enzymatic activity of the commonly used β-glucuronidase extracted from H. pomatia with the same enzyme from Escherichia coli. Our results showed that β-glucuronidases from both sources produced similar results from spotted hyena faeces. We therefore hydrolysed samples with H. pomatia enzymes. HPLC analyses also demonstrated that following hydrolysis the epiandrosterone EIA measured significant amounts of immunoreactive metabolites corresponding to radiolabelled metabolites in both sexes. Additionally, HPLC and GC-MS analyses confirmed the presence of epiandrosterone in faeces of spotted hyenas. The biological relevance of the epiandrosterone EIA was validated by demonstrating (1) a significant increase in fTM levels in response to a testosterone injection within 16 h, (2) no biological responsiveness to an adrenocorticotropic hormone (ACTH) injection and (3) significant differences in fTM levels between juvenile males and adult immigrant males in a free-ranging wild population. Our results clearly demonstrate that the epiandrosterone EIA is a reliable non-invasive method to monitor gonadal activity in spotted hyenas.

The intensity of male-male competition may affect chemical scent constituents in the dark ventral patch of male Iberian red deer

“…Androstanedione is a steroid metabolite and a precursor of both testosterone and estrone, so it might have the function of signalling the testosterone level or the reproductive status of the individual, acting as a powerful signal [25]. Epiandrosterone has been identified as the major testosterone metabolite in a variety of male mammals ( Sus scrofa [59], Macaca fascicularis [60], Cebus capucinus [61], Crocuta crocuta [62], Acinonyx jubatus [63]). It has been used as a gonadal activity indicator and the measurement of epiandrosterone metabolite reliably indicates the testicular endocrinal activity in ungulates ( Giraffa camelopardalis [64], chamois, Rupicapra rupicapra rupicapra [65], Cervus elaphus [66]).…”

Non-invasive assessment of glucocorticoid and androgen metabolite levels in cooperatively breeding Damaraland mole-rats (Fukomys damarensis)

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