Reproduction in the zebra stallion (Equus burchelli Antiquorum) from the Kruger National Park

Reproductive characteristics of free-ranging zebra stallions 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 two to seven individuals. The youngest stallion leading a family group was four years old. On average stallions attain psychological maturity at four and a half years of age, the pubertal interval ranging from age two to four and a half years. The youngest specimen with epididymal spermatozoa was two years old but generally this occurs at three and a half years but behavioural mechanisms prevent mature sub-adult stallions from mating with oestrous mares. Variationin 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 two instances of unilateral testicular hypoplasia and one of bilateral cryptorchidism. Only the latter caused sterility

Some reproductive abnormalities of the zebra stallion (Equus burchelli Antiquorum)

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Gross and microscopic observations of ovarian abnormalities from five Burchell's zebra, Equus burchelli antiquorum, Smith 1841

Five pair of zebra ovaries were submitted to the Onderstepoort Veterinary Research Institute for examination because of unusual uni- and/or bilateral gross appearances. Microscopic findings revealed an accessory spleen encapsulated by the ovarian peritoneum, a case of tuba-ovarian cysts, one example of ovarian aplasia, an example of germinal inclusion cysts and an abnormal follicular haemorrhage related to pressure necrosis of a nearby corpus luteum. Similarities to the ovary of the domestic mare were also seen and some are briefly described.The articles have been scanned in colour with a HP Scanjet 5590; 300dpi. Adobe Acroabt XI was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Keeping the herds healthy and alert: implications of predator control for infectious disease

Predator control programmes are generally implemented in an attempt to increase prey population sizes. However, predator removal could prove harmful to prey populations that are regulated primarily by parasitic infections rather than by predation. We develop models for microparasitic and macroparasitic infection that specify the conditions where predator removal will (a) increase the incidence of parasitic infection, (b) reduce the number of healthy individuals in the prey population and (c) decrease the overall size of the prey population. In general, predator removal is more likely to be harmful when the parasite is highly virulent, macroparasites are highly aggregated in their prey, hosts are long-lived and the predators select infected prey

Home range sizes for burchell's zebra <i>equus burchelli antiquorum</i> from the Kruger National Park

Annual home range sizes were determined for 49 marked zebra family groups in the Kruger National Park. Sizes varied from 49 to 566 sq. km, the mean for the Park being 164 square kilometre. Mean home range sizes for different zebra sub-populations and biotic areas were found to differ considerably. Present herbivore densities have not influenced intra- and inter-specific tolerance levels to the extent that home range sizes have increased. Local habitat conditions, and particularly seasonal vegetational changes, were found to have the most profound influence on the shape and mean size of home ranges. The large home range sizes obtained in the Kruger Park, when compared to an area such as the Ngorongoro Crater, can be ascribed to a lower carrying capacity with respect to zebra, large portions of the habitat being sub-optimal, either seasonally or annually

Pre- and postnatal growth phenomena of Burchell's Zebra <i>Equus Burchelli Antiquorum</i>

Between 1969 and 1972 growth data were collected from 175 zebra Equus burchelli antiquorum and 138 zebra embryos and foetuses from the Central District of the Kruger National Park, Republic of South Africa. Statistical analysis of data indicated no significant difference between body mass of adult stallions (range == 267,3 to 373,3 kg; mean = 318,5 kg; n = 57) and adult non-pregnant mares (range = 272,6 to 386,9 kg; mean = 321,6 kg; n = 51) (t = 0,587). The heaviest zebra had a body mass of 429,4 kilogram. This was a pregnant mare carrying a 35,2 kg foetus. Von Bertalanffy growth curves indicated that shoulder heights in young zebra may reach the adult range by one year of age, the adult body mass range is, however, only attained after three years of age. These curves also showed that age classification of free roaming zebra is only reliable up to the age of about two years, after which individual variation is too great. Stallions were significantly taller at the shoulder than mares (mean = 1,8 cm) (t = 2,032) and neck thickness was the only body dimension showing visible sexual dimorphism in adults. Here the stallion had a neck girth on average 8,1 cm greater than the mare. Regression equations for estimating body mass from body dimensions were calculated by using a standard logarithmic transformation and fitting a linear regression by the method of least squares and also by undertaking standard straight line linear regression analyses. Exponential curves obtained by the first method indicated that growth was not isometric (not linear) and that the ratios of any of the dimensions of length to body mass were con- stantly changing, i.e. growth is allometric. Marked allometric growth differences existed between the two sexes except in the case of the heart girth-body mass relationship. Comparison of growth data from E. b. antiquorum with that of E. b. boehmi from Tanzania (Sachs 1967), indicates that E. b. antiquorum is considerably larger. Body masses differ by an average of 70 kg and 102 kg for stallions and mares respectively. Average birth mass for zebra was 33,7 kg. The largest foetus had a body mass of 39,0 kilogram. Foetal growth curves are provided. The first signs of body stripes occur at between 250 and 270 days of pregnancy (gestation period = 375 days)

Ketamine Hydrochloride - a useful drug for the field immobilization of the Spotted Hyaena <i>Crocuta Crocuta</i>

The use of Ketamine hydrochloride (Vetalar, Parke-Davis) for the capture and restraint of five spotted hyaenas (Crocuta crocuta) is discussed. The wide margin of safety andrelatively short recovery period associated with Ketamine makeit a useful substitute for drugs such as Phencyclidine hydro-chloride (Sernylan) and Succinylcholine Chloride, routinely used for the capture of carnivores

Dentition and Life History of a 16-year-old Known-age Free-living Male Lion<i> Panthera leo</i> (Linnaeus, 1758) from the Kruger National Park

Wear in the dentition of a known-age, free-living, 16-year-old male lion is described and compared to existing age-determination techniques. Aspects of his life history are described as they are in some contrast to what is known of male lions' life history strategies