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The roe deer (Capreolus capreolus) is a seasonal breeder, whose reproduction shows a distinct seasonal pattern with the breeding season (rut) lasting from mid-July to mid-August. Mature bucks show synchronized testicular cycles and transitions between totally arrested and activated spermatogenesis thanks to the peak of testosterone(TEST) between June and July [2]. Recently, hair has proven to be a good non-invasive matrix for endocrinological analyses, providing long-term information [1]. The aims of the present work were, firstly, to quantify hair concentrations of TEST and cortisol (CORT) in wild roe deer bucks hunted during pre and post rut period, using a radioimmunoassay (RIA) methodology, and to look for relevant differences between the two periods, and then to evaluate any possible correlation of such hair concentrations withblood ones and morphometric parameters of the testes. Twenty-eight mature roe deer bucks, were sampled during the hunting season between June 1st and July 15th 2017 (pre rut, n=14) and August 15th and September 30th 2017 (post rut, n=14) in the South-Western Bologna Apennines (Italy). All the animals analysed were killed and immediately transferred to the pertinent biometrical centre, where the personnel collected blood upon jugulation, hair from the dorsal caudal region of the animals and scrotums, including testis and epididymis. For the testicular analysis each testis was isolated, weighed and sectioned longitudinally. Major and minor axis were calculated and for each roe deer the measures were averaged between the two testis, in order to get a final mean volume. CORT and TEST were previously extracted from hair [1] and blood, and their concentrations were determined using a RIA technique. The results show that the testicular volume and weight significantly decreased in the post rut group (p=0.0089 and p=0.0056 respectively); the same happened for blood TEST concentrations (p=0.0008). The blood CORT levels did not show any statistical difference between the two groups (p=0.8336). The hair results showed an increase in TEST levels in the post-rut (p=0.00003), almost double the pre-rut ones. TEST reaches its blood peak in the pre-rut period, therefore it is likely that high hair post rut values are the direct reflection of high blood pre rut values. Differently, CORT levels decrease in the post-rut (p=0.0014), and this may be due to different environmental factors, leading to higher concentrations of hair CORT in the pre-rut. The correlations found by the statistical analyses were in agreement with the existing literature about the fluctuating concentrations of the two hormones in the blood throughout the year and the cyclic growth and reduction of the testis [2]. Moreover, this study represents a first validation for the use of a RIA technique to quantify both TEST and CORT in roe deer hair, confirming the use of this matrix as a good long-term information provider, and giving interesting insights on the physiology of reproduction of this species.