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.
