 Reference Base  Reproduction and population density: trade-offs for the c... |
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Rachlow, J.L.; Berger, J., 1998. Reproduction and population density: trade-offs for the conservation of rhinos in situ. Animal Conservation 1 (2): 101-106, figs. 1-3, table 1
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| Location: |
Africa - Southern Africa - Zimbabwe |
| Subject: |
Reproduction |
| Species: |
White Rhino |
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Zimbabwe. Female reproductive parameters varied with population density. Age at first reproduction for female white rhinos in MNP varied from 6.5 to 11.5 years of age. Using data for all females, age at first reproduction increased significantly with total population density in the year of conception.
A contrast of age at first calving between the low-density (HA) group and the high-density WGP rhinos revealed that age at first birth was significantly lower for HA females (n = 4) than for those in the WGP (n = 9). Mean age at first birth was 7.4 ? 0.4 years in the low-density group and 10.1 ? 0.7 years in the high-density population. This contrast includes only females born during the period of 1982-1994, the time period for which data are available for both groups.
Discussion
Females that reproduce early should gain a genetic advantage over those that delay reproduction. However, early growth and maturation may affect future fecundity or survivorship. The age at which mammalian females reach puberty and begin reproducing can vary markedly with population density. Age at first calving also appears to be sensitive to population density in African rhinos. In black rhinos, age at first birth was 6,5 years in a low-density population in Umfolozi Reserve, South Africa, and 12 years in a high-density population in the neighbouring Hluhluwe Reserve. In MPN, first births occurred at older ages in white rhinos as density increased, and females in the low-density population calved at significantly younger ages than did those in the high-density group.
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