Ovarian activity and pregnancy in the Siberian tiger, Panthera tigris altaica, assessed by fecal gonadal steroid hormones analyses

Feces were collected from two female and one male Siberian tigers, Panthera tigris altaica. Steroid hormones were extracted from lyophilized feces and quantified by enzyme immunoassay. The fecal contents of estradiol-17β (E2) and testosterone in the females and male, respectively, changed markedly throughout the year. The fecal E2 contents of females Nos. 179 and 238 increased at 26.4 ± 8.0 and 28.0 ± 14.2 day intervals, respectively. However, the fecal contents of progesterone (P4) in the female kept alone did not change. In contrast, the other female, which was kept with a male, had increased fecal P4 contents after copulation. The fecal progesterone levels of the pregnant female remained high during her 106-day pregnancy.