Key reproductive parameters of
Roan, Sable and Tsessebe Antelopes
| Seasonal breeding |
Roan breed throughout the year; sable give birth to
calves January- March; tsessebe give birth to calves October-November.
|
| Gestation |
All 8-9 months |
| Age at first conception |
Almost all females conceive after about two years |
| Age at first parturition |
Almost all females produce calves in third year of life
|
| Fecundity (adults) |
All adult females are capable of producing a calf every
year - fecundity of roan may be slightly above unity in
favourable conditions |
| Longevity |
Few animals survive beyond 12 years of age in the wild
|
| Breeding longevity |
Females are probably capable of breeding throughout
their adult life although fecundity may be reduced in
last few years |
| Mortality (juveniles) |
About 25% in average years |
| Mortality (yearlings) |
Females about 5%, males generally higher |
| Mortality (adult males) |
Around 10%, increasing in the last few years of life |
| Mortality (adult females) |
Less than 5% except in last few years of life |
|
Adult sex ratio
|
About 2 females to 1 male depending on hunting regimes
and predation |
Table derived from Erb 1993, Dunham, Robertson & Swanepoel
2003, Dunham and Robertson 2001, Grobler 1974, 1979, 1980,
1981a, Joubert and Bronkhorst 1977, Penzhorn and van der Merwe
1993 and Smithers 1983
There is sufficient similarity in the biological parameters
which determine the population dynamics of roan, sable and
tsessebe to permit a generic population
model to be used to examine their expected breeding performance
under average conditions. The model suggests that under "average
conditions", roan, sable and tsessebe populations could
be expected to increase at a rate of slightly under 14% per
annum when they are below ecological carrying capacity.
However, the term "average conditions" has to be
used carefully. The effects
of late dry season rainfall appear to be critical, affecting
the animals' ability to maintain condition and, hence, survival.
Several theories for he Decline
of Roan, Sable and Tsessebe have been put forward.
|
