Several examinations on the reproductive status of lowland gorillas (Gorilla g. gorilla) at Hannover Zoo

Abstract

AbstractThere as been no reproduction within the Hannover Zoo's gorilla group, although several adult females and a silverback male have been living together for a prolonged period. Therefore, the sexual cycle of three adult females was examined by means of total urinary estrogen excretion, measurement of the urogenital cleft length, ovulation detection with the help of the Subhuman‐Primate‐Pregnancy Test (SPPT), measurement of basal body temperature, semiquantitative blood tests to detect menstruation, and observation of sexual behavior. Fertility status of the silverback male was examined by means of behavioral observation, rectal probe ejaculation (RPE), and testicular biopsy. Sexual cyclicity was demonstrable in two females, whereas the third had an irregular occurrence of estrogen peaks and her menstruation and sexual behavior did not show normal cyclicity. The male's infertility was characterized by absence of any sexual behavior, azoospermia in repeated RPE, unsuccessful treatment with clomiphene, and atrophy of seminiferous tubules in the extirpated tissue.Several factors, such as vitamin E deficiency, humoral dysregulation, testicular hypoxy, and spermatogenic arrest, caused through stress due to inadequate shelter systems, are discussed hypothetically in regard to their possible etiological relevance with respect to infertility in this species.In many cases infertility in the gorilla male is presumably based on a polyfactoral etiology. Analysis of urinary hormone levels in parallel with behavioral studies is still to be tested as a practical method of gaining information on the puberty development of adolescent males and on the fertility status of adult males under zoo conditions.