One of our Facebook fans send us a link to this field study in the Kruger National Park, by Emily Goldberg at Yale.
By Ron Thomson
Here is my insight on the question.
Elephants are “preferential grazers”. That means they prefer to eat grass – when it is green, nutritious and palatable. It also means they eat grass almost exclusively during the rains. This does not mean elephants stop eating browse during the rains – but browse is then a minuscule proportion of their diet. So at different times of the year – depending on the quantity and the quality of the grass that is available – they will eat both browse and grass to varying degrees.
Palatable grass during the height of the dry season, however, is in poor supply (or simply not available) – because many species of animals (in addition to elephants) are either grazers or grazers-and-browsers combined; and by the time the dry season advances there is no palatable grass left at all. And grass doesn’t grow very much – or not at all – during the dry season.
So during the dry season, the elephant’s diet is made up almost exclusively of green tree leaves and the cambium bark of several favourite tree species. Elephants are VERY preferential feeders – selecting favourite tree species whenever they feed to the point of driving those trees to the point of local extinction (whilst not feeding very much on other species).
I don’t think, therefore, that there is any confusion regarding “The factors that influence the elephant’s diet”. If ice cream is your favourite food, and you have lots of ice cream available to you, you will eat ice cream! The elephant’s diet is governed by exactly the same thing. They eat WHAT they can find to eat when it is available – except that they will always eat green grass preferentially. They are, however, highly selective in the trees that they will eat, too – bypassing many tree species to get to those that they like to eat the most.
And the milk of lactating mother elephants varies considerably during the different season of the year. During the rains – when elephants are eating almost exclusively grass – elephant’s milk is sweet and palatable – very much like rich cows milk.
During the height of the dry season, however, when the elephant’s diet is almost exclusively the bark of trees – like the ubiquitous Mopani – their milk is greatly astringent and quite unpalatable by man. How and why baby elephants drink their own mother’s milk at the height of the dry season, therefore, is an enigma to me. They do so, of course, because they have no other option. How do I know all this? I have drunk elephant’s milk many, many times right through all the different months of many, many years (in the 1960s and 1970s)
There is no correlation between the elephant’s diet and the damage they do to trees; and a great deal of the most extensive damage to trees is carried out by teenage bulls – and young adults – showing off their respective strengths to their peers. That is how elephant bulls determine their rankings in bull society. And very rarely are any of the trees so damaged eaten by the destructive culprits.
If you want to know more about this phenomenon – and host of other reasons why and how elephants damage trees – you should get hold of my book “ELEPHANT ‘CONSERVATION’ – The Facts and Fiction”. Elephant bull density, however, is a major factor in the numbers of trees the bulls damage when organising their rankings.
I hope this helps you to understand the problems you are trying to solve. Don’t get too swept away by science. Most of the answers you are seeking can be found using simple common sense.
John Rance also shared his opinion.
As Ron says, common-sense rules. When there are too many elephants for their habitat to support, well … there are just too many elephants and they will destroy their habitat unless their numbers are reduced. From a number of previous studies and even a simple visual analysis, one can determine that current numbers are way in excess of what all Southern African protected areas can support.
No amount of scientific studying will gainsay this. When (not if) the numbers are reduced to common-sense sustainable levels, either through man’s intervention, or nature’s wholesale decimation of elephant herds when their habitat can’t support them sustainably, then scientific studies can be used to determine carrying capacities. But this has all been done in the past.
If a protected area was scientifically determined to enable a carrying capacity of, say 5500 elephants, but the population was only reduced to, say, 7500, then the habitat destruction just took longer. However, if that area is now carrying, say, 25’000 elephants, the habitat destruction is much faster and the elephants’ demise much closer in time.
The problem with allowing nature to do this, instead of man, is that the resultant habitat destruction will only be able to support a much lower number of elephants for hundreds if not thousands of years and certain species of plant life and other animals, insects, and birds will be destroyed and may never recover above the predation level.
The decision not to cull elephants to sustainable population level is an environmentally criminal madness, fuelled by anthropomorphic emotion instead of logic and common-sense.
We must all just hope that the likes of TGA’s efforts, driven by Ron’s passion for sustainable conservation, will change things before total destruction. One can’t say “before it’s too late” because it’s already too late.