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

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.