Hair Testosterone and Cortisol Concentrations in Pre- and Post-Rut Roe Deer Bucks: Correlations with Blood Levels and Testicular Morphometric Parameters

SIMPLE SUMMARY: The roe deer is a very common wild species in Italy and shows peculiar reproductive characteristics. Sexually-mature males, called bucks, show a complete interruption in spermatogenesis during the cold seasons. The mechanisms behind such interruption are still partially unknown. Hair is a good biological sample, easy to obtain while minimizing stress, for endocrinological analyses that may provide information regarding such mechanisms. The aim of the work was to quantify and compare hair concentrations of testosterone and cortisol in wild roe deer bucks hunted during the pre- and post-rut period (mating season). The secondary objective was the evaluation of possible correlations of such hair concentrations with blood and morphometric parameters of the testes. Testosterone significantly increased from the pre- to post-rut period, while cortisol significantly decreased. The correlations with blood and testicular parameters resemble what is already described in the literature. Overall, this study represents a first report of the quantification of testosterone and cortisol in roe deer hair, and may provide interesting insights into their reproductive physiology. ABSTRACT: The roe deer is a seasonally breeding species with a reproductive cycle regulated by endogenous rhythms and photoperiod-sensitivity. Sexually mature bucks show hormonal and testicular activation during the reproductive season, with a peak in the rut period, and following gradual involution. Hair is a good matrix for non-invasive endocrinological analyses that provide long-term information without being influenced by the hormones’ pulsating release patterns in blood. The aim of the work was to quantify hair concentrations of testosterone and cortisol in wild roe deer bucks hunted during the pre- and post-rut period, using a radioimmunoassay methodology, and to look for differences between the two periods. The secondary objective was the evaluation of possible correlations of such hair concentrations with blood and morphometric parameters of the testes. Both hormones showed statistical differences, with opposing trends, when comparing the two periods: testosterone increased while cortisol decreased. The correlation analysis was in agreement with existing literature regarding metabolism/actions of these hormones and testicular morphometric parameters. This study represents the first report of the use of radioimmunoassay techniques to quantify testosterone and cortisol in roe deer hair, and may provide interesting insights into their reproductive physiology.