Reproduction in the Zebra Stallion ( Equus Burchelli Antiquorum ) From the Kruger National Park

Abstract

Reproductive characteristics of free-ranging zebra stallions in Kruger National Park, South Africa are described using data collected from 270 cropped specimens and field observations of live animals. Socially zebra populations comprise coherent family groups dominated by a single stallion and consist of 2-11 individuals including foals. Excess stallions remain solitary or form stallion groups of 2-7 individuals. The youngest stallion leading a family group was 4 yr old. On average stallions attain psychological maturity at 4 1/2 yr of age, the pubertal interval ranging from age 2-4 1/2 yr. The youngest specimen with epididymal spermatozoa was 2 yr old but generally this occurs at 3 1/2 yr but behavioral mechanisms prevent mature sub-adult stallions from mating with estrus mares. Variation in testicle mass and seminiferous tubule diameter indicates that adult stallions have a reproductive peak during the summer (wet season) which coincides with the cycle of the mare. Genital abnormalities included 2 instances of unilateral testicular hypoplasia and 1 of bilateral cryptorchidism. Only the latter caused sterility.