 Reference Base  How vulnerable is the black rhino? A genetic and demogra... |
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| Location: |
World |
| Subject: |
Ecology - Population |
| Species: |
Black Rhino |
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Analysis of demographic factors indicate that wild black rhinoceros populations remain stable (i.e. sex ratio and age structure do not change dramatically) even if they experience ecological threats such as competition, predation, droughts and fire. Poaching has a negative effect on the sex ratio and age structure, however, and will result in a serious decline in effective population size.
A demographic extinction model (DEMM) was written to determine the persistence time of black rhinoceros populations. The model uses a Leslie matrix with age-specific fecundity and mortality data. The results of DEMM compare well with other extinction models, e.g. Vortex and Goodman's models. All three models (based on the small population aproach) suggest that demographic and environmental stochasticity will cause the three black rhinoceros populations (captive, Mkuzi and Tsavo) to go extinct within 300 years. This highlights the urgent need for intensive management of the remaining black rhinoceros populations. The population persistence analysis model (PPA) was also used to predict the persistence time of larger black rhinoceros populations. PPA is based on the declining population approach and only requires census data which makes this model more accessible to managers of rhinoceros populations. Ideally, PPA can be used to prevent the small population situation by identifying a decline in a population at an early stage. If a population is already classified as 'small', extinction models such as DEMM, Vortex and Goodman, which address the problems faced by small populations, are invaluable. Managers of black rhinoceros populations can use extinction models as valuable tools to assist them in making scientific decisions for the conservation of the species.
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