[Variations in blood testosterone levels of prepubertal foxes and during the seasonal genital cycle of the adult male fox (Vupes vulpes) in captivity].

Plasma testosterone levels have been determined by radioimmunoassay on peripheral venous blood samples of young and adult foxes at different times of their genital activity. In the cub, the testosterone levels increase from November to January; at this time, the young is pubescent. In the adult, the testosterone levels are low from April to November. At this time, the levels increase and reach a maximum value from December to February, which is the mating season. Some high testosterone levels observed in summer prove that the endocrine activity of the testis persists during the out-breeding season.