There is concern that despite fact that humans have reduced the critically endangered black rhino numbers by well over 90 percent in the last century, rhino’s may actually be suffering the effects of more recent population increases in some reserves.
Indeed, the vital south-central black rhino (Diceros bicornis minor) population in the entirely fenced Hluhluwe-iMfolozi Park, South Africa, could be suffering the effects of over-population (i.e., reduced population performance). Anecdotal evidence collected from field rangers suggests that rhino home ranges may be getting bigger and calving periods longer, which can indicate a population is struggling. Unfortunately, the quality of data remains inadequate to be confident of this assumption. For example, previous studies have used home range inflating fortuitously gathered sighting locations to conclude dramatic increases in black rhino range size i.e. supporting the overpopulation argument. However, results from my stratified sampling of radio-tagged rhino shows that average home range sizes have not in fact increased over the last forty years. Thus, the debate about the status of Hluhluwe’s strategic donor population continues. In the context of significant increases in rhino poaching (i.e. a dozen a year in 2007 to over 400 now) in South Africa, understanding how these prehistoric mega-herbivores behave and what effects their population dynamics demands attention.
Africa’s oldest reserve, rife with rhinos
Essentially I think we don’t know enough about the ecology of the rhinos, and so I am intensively tracking the rhinos to try to find out more. They appear to have strong social bonds to their individual rhino neighbours, so its very hard to understand how taking out other rhinos affects the ones left behind. The Park which is the oldest in Africa (c. proclaimed 1875), has acted as the key base for both black and white rhino populations since the 1960s when D. b. minor numbered as little as 100 individuals – all found in Hluhluwe.
When numbers bottomed in the 1960’s, the Natal Park’s Board- now Ezemvelo KwaZulu-Natal Wildlife (EKZNW), began ‘Operation Rhino’ as a large-scale initiative to bolster their populations. They pioneered large animal capture techniques, improved security and meta-population management (fencing off animals and transplanting small percentages to different areas), repopulating large swaths of southern Africa with rhinos.
There are now more than 1600 D.b. minor and southern white rhino (Ceratotherium simum simum) number also having bounced back, from a small population in the park (c. 50) to now more than 17000 across the southern part of the continent.
There is no doubt that the repopulation and range expansion program has been enormously successful and brought black rhino back from the brink of extinction.
Taking another step forward for African rhinos
There have been more problems recently with poaching, largely because disposable incomes have increased in Asia and the demand and ability to obtain horns has gotten so high and the price so dear, that poachers can now afford to fly helicopters into parks to find rhinos. Operation Rhino, initiated from HiP, has essentially been one of the world’s most successful large-animal conservation efforts in the world, and there is an argument to be made that if they hadn’t developed the techniques they did in the park, none of the other rhino populations in Africa would have survived either. The time has come, however, to consider what happens to those left behind, especially if too many rhinos are taken out when the population is not performing well?