Right now this month there is a herd of 5 young male Sable that regularly visits the firebreak between the Sabi Sands and the KNP. They like to come for the fresh shoots that have emerged in the firebreaks.
For years I have thought about the reasons why there was a population decrease. And from reading various articles etc it does seem that its a combination of factors rather than a single event. But its not just these 2 mammals that have had extreme reductions in population size. Blue Wildebeest used to occur in migratory herds of 10 000 and more. There are barely 10 000 in the park today. Species composition has varied in areas and there seems to be an overall decrease in plains mammals like your wildebeest.
Following a very interesting conversation with a reputable South African Zoologist I was intrigued at his reasons for the population declines/shifts of the various mammal species in the KNP:
Basically he explained that due to water abstraction for forestry, farming and human consumption outside of KNP (mostly to the West) the rivers run drier through the KNP than historically. The overall water table height is on average lower and as a result the KNP plant communities have shifted to favouring species that are more drought adapted. This is not to say that any plant species will become extinct but rather that those that are adapted to drier conditions will become more abundant.
I have noticed this in Sabi Sands and KNP to quite a large extent where 20 years ago many open areas or partially open areas have now become clogged with your Combretum and Terminalia species for example. Especially around Talamati and South from there in the Western areas of KNP.
I would love more intense studies to be done on historical vs present plant communities in the KNP and my personal opinion for what its worth is that no matter what we do in management of the KNP the greatest problem lies with the management of water outside the park. Millions can be spent opening and closing waterholes or whatever else but at the end of the day your plant communities are going to have one of the biggest says in determining which species can live in which areas and if water abstraction outside the park is in fact the cause of these shifting mammal populations then a scary and almost impossible task lies ahead in better management of water resources outside of the park.