Variation of plasma sex steroid concentrations in wild and captive populations of Hermann’s tortoise (Testudo hermanni hermanni) in Southern France

Abstract Plasma levels of sex steroids in both males and females of the endangered Hermann’s tortoise ( Testudo hermanni hermanni ) were measured throughout their active period in a wild population in the Massif des Maures, France, and in a nearby captive population at Le Village des Tortues in Gonfaron. Both plasma progesterone and testosterone were elevated in males at emergence from winter dormancy, and plasma progesterone levels were significantly higher in wild than in captive males. Plasma testosterone in males then fell to the lowest levels (10 ng ml −1 ) during the nesting season from April to June followed by an elevated plateau during summer, with levels reaching 80 ng ml −1 , presumably concomitant with spermiogenesis. Plasma testosterone increased in all females during autumn, an indication of follicular growth, and remained high on emergence from hibernation, to peak during April, although levels were lower in the captive population. Plasma progesterone also peaked during April and May, presumably related to ovulation, but, again, these changes were less marked in the captive than in the wild females. Measurements of testosterone, progesterone and 17β-oestradiol in the captive females during their period of oviposition in spring suggested that some females did ovulate and lay eggs, whereas others did not. Differences in sex steroid levels between captive and wild populations of Hermann’s tortoise may indicate a problem with ovulation and/or with stress in a proportion of captive females.