Studies on the biology and productivity of the giraffe giraffa camelopardalis

Abstract

This study was carried out in the eastern Transvaal Lowveld in an area 2 with a giraffe population density of 2,6 per km . Lions are the only predators and it was estimated that 48% of the calves die in their first year. The sex ratio departs significantly from unity in favour of females. Plant fragments in the rumen were identified. Giraffe subsist on the leaves of trees and shrubs, though fruit, flowers, twigs and grass were also utilised. Marked seasonal changes in the plant species selected were determined by availability and different habitats were utilised accordingly. Chemical analysis of rumen content showed correlations of nutritional value with species eaten and seasonal phenological changes of the vegetation. Tooth eruption, wear and incremental layers in the cementum were found to be suitable criteria for age determination. Total body mass was measured and carcasses dressed out at 61,9% for males and 56,6% for females. Lower mass and lower proportion of fat was found in the dry season. Meat yield was similar to other African ungulates, buttock and bone proportion was high, but fat was low. A gestation period of 457 d and birth mass of 102 kg (higher than in the literature) was used to determine the age of foetuses whose growth was similar to other uniparous mammals. Postnatal increase in mass, height, length and chest girth followed the usual mammalian growth curve. Mass could be predicted from buttock or foreleg mass or from body measurements. There is evidence that hypertrophy of the foetal testis occurs. Parameters of male sexual function were correlated with age, but no seasonal effects were apparent. Puberty was found to be dependant on physiological status. Androstenedione was the dominant testicular hormone in the foetus and testosterone ·in the adult. Most conceptions occurred du~ing the humid months of the year when conditions are good for the females. Vesicular and haemorrhagic follicles and corpora lutea were common in foetal ovaries. Numerous corpora lutea were also found in immature ovaries, but they regressed at puberty. The corpus luteum of pregnancy underwent a decrease in size in early gestation followed by an increase to term. Both ovaries are equally active, implantation is ipsi1ateral and the placenta is polycotyledonary of the syndesmochorial type. Gonadotrophic activity could not be demonstrated in the urine of pregnant females. Lactation endured for about 13 months, the milk was relatively rich but its composition changes with time. There was a reduction in stomach fill in late gestation but lactating females had a significantly greater fill than others.