Category: Facts Matter

More on the Kruger National Park Elephants.

On the subject of elephant carrying capacities.

Why is the elephant carrying capacity of a game reserve important? It is important because that is the maximum number of elephants the game reserve can sustainably carry without them causing permanent damage to their habitat. This is not difficult to understand but still people-who-purport to care about such things STILL haven’t come to terms with this criterion. If you don’t believe me, just ask the scientists who are responsible for the management of elephants in a national park. I have worked in the field of elephant management in African national parks for getting on for 55 years and I still find that people everywhere, people who should know better, avoid discussing the subject of elephant carrying capacities – and so they deny the subject its rightful level of wildlife management importance.

Just at the moment our social media has been flooded by the subject of elephant management in Kruger National Park and those in this conversation who purport to know what they are talking about  refer to Kruger’s elephant carrying capacity to be 7000 – when it is nothing like that number.  So, lets have a look at “numbers” in this regard and mix it up with some historical happenings.

Elephant populations have the capacity to double their numbers every 10 years – and that happens  when the population has an annual incremental rate of 7.2 percent.  So, what is Kruger’s elephant carrying capacity? And what is its annual incremental rate. We have to know these kinds of numbers if we wish to determine just what is happening to Kruger’s elephants every year, and what we need to do – management-wise – to create conditions of which we approve.

Management is the action that man takes to achieve a desired-by-man objective.  And what does man desire for Kruger National Park with respect to his management of the game reserve’s elephants? Man desires to maintain a population of elephants in Kruger National Park that does not destroy its own habitat or the habitats of any other species. And whilst he is doing that, he also has to make sure that none of the other herbivorous animal populations in park are destroying other species’ habitats either.  He also has to make sure that the elephants are not destroying the physical nature of the habitats – such as killing off all the big trees – because that one elephant action will cause the extinction of the big eagle species, and the vultures, which would then not be able to breed.

When the culling era began in Kruger – in 1967 – the habitat’s elephant carrying capacity was not known  (and nobody was prepared to discuss that subject at the time).  Instead, an arbitrary decision was made during the culling era to reduce the game reserve’s elephant numbers down – to 7000 – at the end of every year. And everybody began to think that 7000 was the park’s elephant carrying capacity. And that number was on everybody’s lips. But 7000 was NOT the carrying capacity number at all.  How do we know that? Because at the end of every year – when the number of big trees in the Satara Top Canopy Tree study were counted, it was discovered that the tree numbers in the study area consistently shrunk  in number: For example:

The expansive Satara Tree study started off with, on average, 13 trees per hectare in the initial experiment; and multiple plots

In 1967 (the year the culling started) there were, on  average, 7 trees per hectare remaining in the Satara areas and every year the elephants were religiously reduced to 7000 in number. Yet in 1973 the average number of trees in the Satara study area had been reduced to 3 trees per hectare; and by 1981 the average number of trees at Satara had been reduced to 1.5 trees per hectare; and by 1994 there were no trees at all left standing in the Satara study area. Now, if 7000 really had been the elephant carrying capacity figure for Kruger then the number of trees left standing at Satara would not have shrunk below 7 trees per hectare; and then to nothing.  Hence we can say with absolute confidence that 7000 was NOT Kruger’s elephant carrying capacity figure during those 27 “culling years”.

In those years (1960s & 1970s) I worked out that Kruger’s elephant carrying capacity was probably 3 500 (+- 500). How did I come to that figure? Well, we started off the Satara Top-canopy Tree study with, on average, 13 top-canopy-trees per hectare (throughout all the study area compartments). And all those study plots had been undamaged by elephants since 1944. And no trees were reported to have been damage by elephants throughout the 1950s either. However, it was reported that the Aloe Marlotii had been wiped out by elephants in 1959 – but there was no record of any top canopy trees being damaged in the 1950s.

The first ‘trees’ to be damaged were reported in 1965 when the average number of trees left standing in the study plots had dropped to 9 trees per hectare. That same year the numbers of elephants in the park (measured from helicopter counts) amounted to 7000 (ref. Rocco Knobel). And the culling started in 1967 (at which time the Satara tree count had been reduced, on average, to 7 trees per hectare). Thereafter Satara tree counts were carried out in 1973; 1981 and 1994 (The results of those counts is recorded above.)

I was then faced with trying to work out the elephant carrying capacity from all these figures and my calculations were, admittedly, not fully mathematical.  For example, I assumed that the Kruger elephant herds were doubling their numbers every ten years – which is fairly probable but that deduction was not mathematically calculated. And I assumed that because no Satara trees had been recorded as being damaged during the 1950’s decade that the recorded number of standing trees throughout the 1950s roughly reflected the elephant carrying capacity figure for that period. And because we know that Kruger elephant herds numbered 7000 in 1965 (accurate helicopter count), and because the elephant numbers in 1955 were half the number that they were in the 1965 (using the figure 7.2% increment), that the elephant herds (on average) numbered 3500 throughout the 1950s.  Ipso facto, the elephant carrying capacity figure throughout the middle 1950s must have been that number – 3500 (which I guessed could be expanded to 3500+/-5000).

Many people will no doubt find considerable fault with this ideal – and/or the way I have calculated it, BUT I contend that it is the nearest that anybody is ever likely to get to the ACTUAL elephant carrying capacity figure for Kruger National Park. One thing the carrying capacity figure is NOT – it is NOT 7000. And elephant carrying capacity is not an easy problem to resolve.

Ron Thomson  CEO- TGA