The Elephants of the West Coast Fossil Park
Patricia A. Groenewald
If you’re familiar with South Africa’s topography and geography, you may find the idea of elephants roaming among the dunes and strandveld shrubland of the West Coast almost ludicrous.
“It can be quite difficult to imagine large, lumbering elephants in this sparsely clad environment when we are more used to the images of elephants in the habitats of the Kruger or Addo Elephant National Parks. We can even picture them in the forests of Knysna, especially when reading stories such as those by Dalene Matthee,” says Patricia Groenewald, a PhD candidate, in the Department of Archaeology at the University of Cape Town (UCT).
The fact is, we don’t think of elephants in Fynbos, even though they lived in this area until the late 1800’s, and as fossil evidence found at the West Coast Fossil Park suggests, they were here for a very long time before that.
Home to three species
Five million years ago, Loxodonta cookei (similar to today’s African elephant), Mammuthus subplanifrons (the earliest kind of mammoth) and Anancus capensis (an extinct kind of elephant known as a gomphothere), made the Langebaanweg area their home. Although, at the time, the climate was subtropical and the vegetation somewhat different, fynbos was already part of the environment.
Being the largest mammal on the planet with infamously poor digestive systems, elephants (and their ancestors) have had to eat a lot to get enough nutrition. How, then, did these three species of mega-herbivore get enough to eat when they were living in the same place with similar vegetation to what we see around us today?
Were they grazers, browsers, or a mixture of both? Did they eat different food to avoid competition, or did they fight each other for the same food?
These are some of the questions Groenewald set out to answer in her honours research.
“To find answers, I got permission from the South African Heritage Resources Agency (SAHRA) and Iziko Museums of South Africa to analyse the stable carbon isotopes from the enamel of thirteen A. capensis, twenty L. cookei and three M. subplanifrons fossil molars (the teeth used for grinding food),” she says.
“The tooth enamel is the hard outer part of the tooth that preserves well when it fossilises, so it is a useful part of the animal to study when you want to learn about what it ate.”
But first… What is a stable isotope and why can we use it as a proxy to reconstruct the diets of extinct animals?
In the picture of the Periodic Table (Figure 1), you’ll see that the most common type of carbon has six protons, six neutrons and six electrons, and it is in the sixth position on the periodic table. Its position in the table is determined by the number of protons, so even if the number of neutrons changes, it is still carbon. You may be familiar with the rare radioactive isotope of carbon, 14C, which decays to nitrogen over time and can therefore be used for radiometric dating. What you may not be aware of, is that there are two stable (i.e. non-radioactive) isotopes, 12C and 13C. These are used for dietary reconstruction.
The seven neutrons of 13C make it bigger and heavier than the more common 12C, so it moves through biological systems with more difficulty.
Plants actively exclude it during photosynthesis, and some (known as C3 plants) are more efficient at doing so than others (known as C4 plants).
Most of the plants in the Western Cape, including the grasses, are C3 plants. In summer rainfall areas, it is easier to distinguish browsers from grazers, because the browse is made up of C3 plants and the graze is made up of C4 grasses.
“In the Western Cape we must rely on environmental differences – browse growing in the shade takes up less 13C, while grass growing out in the open takes in a greater amount of this isotope,” she continues.
“When animals eat the plants, they take in the ratio of 13C to 12C and store it in their body tissues, so we can see what kinds of plants they ate.”
Questions answered
The results of Groenewald’s analysis showed that A. capensis had the smallest range and probably preferred shady, wooded parts of the Langebaanweg environment where it mainly browsed.
L. cookei and M, subplanifrons, on the other hand, spent more time in the open, and ate a mixture of browse and graze, much like modern elephants.
“By partitioning the resources available, as happens in today’s ecosystems, the three species of elephant were able to co-exist with each other and the other animals of Langebaanweg, and the dietary flexibility of Loxodonta may have contributed to the survival of this genus into modern times,” concludes Groenewald.
These are just some of the fascinating creatures whose fossilised remains have been found and studied at the West Coast Fossil Park. Come and join us for a guided tour and find out more about this vibrant land before time where saber-toothed cats, short-necked giraffes, hunting hyenas and African bears once roamed.
