Similarity in Ejaculate-Endocrine Characteristics in Captive Versus Free-Ranging Cheetahs of Two Subspecies1

Abstract

Ejaculate-endocrine characteristics were measured in 23 captive cheetahs (Acinonyx jubatus jubatus) in North American zoos and in 8 free-ranging cheetahs (A.j. raineyi) in eastern Africa (Tanzania). A standardized electroejaculation protocol was used, and numbers of motile spermatozoa were similar (p>0.05) between groups. Of the spermatozoa collected by electroejaculation, 70.6 ± 3.3% and 75.9 ± 4.4% were morphologically abnormal in the captive “North American” and in the free-ranging, eastern African populations, respectively. Adrenal activity, as measured by an acute, temporal rise and fall in serum cortisol levels during and after electroejaculation, was no different (p>0.05) between groups. Although serum luteinizing hormone (LH) levels were less (p<0.05) in the free-ranging than in the captive animals, serum testosterone concentrations were similar. The data indicate that the comparatively poor reproductive performance of cheetahs maintained in zoological parks is not attributable to a captivity-induced response afflicting the male. Furthermore, there is no evidence that ejaculate/endocrine characteristics differ between the two subspecies. Because adrenal/gonadal activity and the number of pleiomorphic spermatozoa are similar between the test groups, the results suggest that spermatozoal diversity originates as a result of the extreme genetic monomorphism observed universally in the species.