Evaluating herbivore extinction probabilities in Addo Elephant National Park, South Africa
Population extinction evaluations, based on the model developed by Dennis et al. (1991) that did not take density dependence into account and that were based on census data, suggest that many of the herbivore species in Addo Elephant National Park (AENP) are vulnerable to local extinction. As a result of low abundance, grysbok and bushpig populations are likely to become extinct within the next ten years. Species such as the common duiker, eland, buffalo, ostrich and bushbuck are likely to go extinct within the next 60 years, whereas populations such as the black rhino, kudu and red hartebeest appear less vulnerable and display an insignificant probability of local extinction. This conclusion was supported by the absence of discernible density-dependence effects in all but one of the species included in the analyses. In addition, population variance parameters (σ 2 of herbivore species from AENP, were larger than those recorded from the Kruger National Park and various elephant populations from South Africa. These data suggest that strict adherence to the management objectives, by managing for increasing mega-herbivore populations (elephant, black rhino) in AENP may have been responsible for increasing the risk of local extinction of other herbivore populations. Consequently, should the objectives of AENP be amended to incorporate broader biodiversity objectives, the recent extension of AENP, which increased habitat heterogeneity in the Park, may prove timely.
Key words: extinction risk, census.