Left – Leopard – Top right – Oldevai Gorge, bottom right – crocodile
The Serengeti is perhaps the last place on earth, excluding Antarctica, where nature reigns supreme. Formed during a period of intense seismic upheaval, which occurred at much the same time as the fabulous Ngorongoro Crater was formed, about 3 million years ago, the area was dominated by several volcanoes.
Volcanoes differ one from the other by the intensity of their eruptions, dictated by the consistency and amounts of gas and water vapour in their magma, or lava. There are several types of volcanic eruptions and those that occurred in East Africa were “Plinian” eruptions caused when a gas in the magma, the liquid rock that wells up from the earth’s white hot mantle, is suddenly released and thrown out in minute droplets with incredible force – similar to the effect you get when a bottle of fizzy water is shaken and then opened. One of the other most common types is the “Hawaiian” eruption when lava flows like white hot treacle forming dense beds of solid rock as they cool.
The event that created the Serengeti was caused by a series of intense Plinian type eruptions hurling dust and ash high into the stratosphere. This vast burden of volcanic ash settled over the plateau below and briefly smothered animal and plant life; but volcanic ash is full of fertility and in the period between eruptions, something in the region of tens of thousands of years, plants and animals recolonized the plateau.
Several millions of years ago a party of Hominids, the primate line of mammals and one of our most distant biped ancestors, walked across a stretch of damp volcanic ash, which hardened in the fierce tropical sun leaving behind a perfect imprint of their footprints – as well as the footprints of a number of the animals that shared this developing landscape. The ancestors of modern humans are hard to identify, but the footprints found at Laetoli indicate they had come a long way from their tree dwelling primate forebears.
Zebra on the move
The soils of the Serengeti are fertile but thin, in some places less than a metre over the bedrock, but perfect conditions for that master plant coloniser “grass”. Dense grass encourages large populations of grass-eaters, but as the rainfall pattern on the flatlands is somewhat inconsistent the herds of wildebeest, zebra and gazelle soon strip the thin soil bare and have to migrate following the rains and the new growth of grass. The herds digest those parts of the grasses they need and leave behind a liberal supply of droppings; manna from heaven for dung beetles, unwitting experts in the recycling of the herbivores’ leftovers.
One of the fascinating facts about grasses is their ability to resist grazing pressure in the long-term. The foliage above ground can be cleared by grazing and even by fire, but the roots and the growing points beneath the surface of the soil are protected, ready to grow as soon as the rains return; creating a perfect circular migratory cycle for the vast herds of grass eaters and predators such as leopards, lions and hyenas that depend upon the herds for their existence.
Elephants and hippos, giraffe and Thompson’s gazelle all depend upon the annual rain cycle too; and the gathering together of these creatures in astonishing numbers on the Serengeti and along the Mara River makes for the most wonderful wildlife experience. The Crocodiles that lie in wait may have not have had a meal for six months, but now, as the first wildebeest and zebra splash into the turbid flow the crocodiles close their jaw and propel themselves into the river. In spite of their huge size (many exceed 5 metres in length) they are masters of ambush with a lineage that goes back to dinosaur times surviving the great the great extinction 65 million years ago. Lying on the sunny sandbanks, mouths agape waiting for the next meal, you could be mistaken for thinking they are dinosaurs.
My next trip is to South Western Africa……