If you approach the Serengeti from the south-east your first view of the plains will be from the slopes of the Olbalbal escarpment. In front of you, northwestward, as far as the eye can see, stretch the open grasslands: to your right the ridges of the Gol mountains, behind you the Ngorongoro Crater highlands, and all around the wide skies of Africa.

As you drop down the escarpment you will see that the plains are covered with short grass, even at the height of the rainy season. These short-grass plains extend beyond Olduvai Gorge, famous for the skulls of early man which have been found there, and across the boundary separating the Serengeti National Park from the Ngorongoro.

The plains are remarkably productive during the rainy season; however, because there is no permanent water in these short-grass plains and because the grass withers at the onset of the dry season, much of the wildlife can only live here when there is a supply of surface water lying in hollows and natural depressions. This is particularly true of the wildebeest and zebra, both of which need to drink regularly.

During the rainy season months, from November through May, these plains are the feeding ground of a staggering number of animals: 1.3 million wildebeest or white-bearded gnus, nearly 200,000 Burchell's zebras, over a quarter of a million Thomson's and Grant's gazelles as well as ostriches, eland, topi, hartebeest and the predators, both great and small, who follow the herds.

The Wildebeest is the dominant herbivore in the Serengeti ecosystem. The main migratory population ranges a region of 25,000 sq km, of which about two thirds is protected in the park, the Igorongoro Conservation Authority Area and the Kenya Maasai Mara Reserve, the rest lying in the adjacent regions of Arusha and Shinyanga.

Why is the wildebeest the dominant herbivore? This animal has evolved a number of adaptations that enable it to exploit these environmental conditions more efficiently than competing herbivores. With its wide row of incisor teeth the wildebeest can harvest more grass per mouthful than practically any associated grazer.

However, large concentrations quickly exhaust a pasture and so wildebeest aggregations have to keep moving. Thus the migration is a continuous quest for greener pastures and water takes the wildebeest over an annual circuit of approximately 800 kms and covers a much greater distance when daily local movements to and fro are taken into account.

The annual wildebeest breeding season or 'rut' often coincides with the migration off the plains. In a period of only three weeks around 90% of the cows, some 400,000 wildebeest, are bred. It is fascinating to see and hear thousands of territorial bulls, with as many as 280 per sq km, rounding up cows, cutting out bachelor males and bashing heads with territorial neighbors in an all-out effort to breed with as many females as possible.

Eight and a half months later the cows drop their calves, preferably on the shortgrass plains. The wildebeest calving season is another outstanding spectacle. Unlike most antelopes who seek cover when giving birth, pregnant wildebeest gather on the most open terrain available and dozens of calves may be born every morning on these calving grounds. Calves can stand within 7 minutes on average, and remain with and dependent on their mothers for at least six months, and often up to a year. Cheetahs and wild dogs can easily run down older calves, but hyenas and lions look for new ones. After about two days the calves are so hard to catch that the spotted hyenas the main wildebeest predator, seldom bother with them. The wildebeest's short calving season, something unusual in the tropics, seems designed to surfeit predators at one time and not give them a steady supply of calves throughout the year.

There is a general movement off the plains as soon as the grasses lose their green flush. As the dry season intensifies, the population moves further north and west toward Lake Victoria into areas where there is permanent water and thunder storms are most likely to occur out of season. Toward the end of the dry season in July most of the population have ended up in the Kenya Mara.

The most impressive and probably the most reliable migratory event is the mass movement off the Serengeti plains that occurs at the beginning of the long dry season, typically May or June. Lines and columns of wildebeest up to 40 km long have been observed (from the air) heading southwest, north or west as the wildebeest trek to the woodland zone.

The Burchell's Zebra, although outnumbered six to one by wildebeest in the Serengeti, are still obvious participants in the migration. They move in large aggregations, which consist of family units containing up to a dozen females and young, and bachelor herds of mainly immature males. Each family is controlled by a stallion; who defends it both against potential rivals and against predators such as hyenas and hunting dogs. Foals are born in all months except the dry season, but there is an annual peak in December/January. Mares also cooperate in defending the family and especially protect foals against predators. This group-defense is so effective that hyenas prefer to hunt in packs for zebras, whereas they usually hunt singly for antelopes.

The stripe pattern of every zebra is different, making individual recognition comparatively easy. Zebras are very conspicuous in broad daylight, but at night, dawn and dusk-the hours when most predation occurs-the stripes seem to blend and zebras become as hard to see as grey or tan animals.

While the great herds are in the shortgrass plains they are especially hunted by lions, cheetahs, hyenas and packs of African hunting dogs.

African Hunting Dogs are mud and mustard colored with black and white patches and large, round ears. They live in packs of 6-20 animals and have ranges up to 800 sq kms. They are efficient hunters and kills may be gruesome to watch. Their hunting success rate falls off dramatically when the migratory prey disappears from their range.

Each pack has a dominant breeding pair and up to 16 pups may be born in one litter. The pups are kept in dens for about 12 weeks until they are old enough to follow the adults, meanwhile members of the pack supply pups with food. The pups beg for the food which is then regurgitated by the adults. Pup mortality is about 80% as dens are often flooded during the rainy season.

In many parts of East Africa, the Hyena is rarely seen during the daytime, but in the Serengeti they may frequently be observed lying at the mouth of their dens in bright sunlight. At night their whooping cry can often be heard because they are most active after dark. Hyenas have the reputation of being scavengers but they frequently hunt and kill their own food, and it is not uncommon for lions to steal their kills. When a pack of hyenas has pulled down a zebra or wildebeest it is only a matter of minutes before all evidence of their meal has disappeared.

Hyenas live in clans which vary in size from 10 to 100 animals, and occupy a recognized territory. However, a sizable number of hyenas move with the great herds of wildebeest and zebras as they search for grazing and water around the Park.

Cheetahs can be found throughout the Park, but more easily observed animals are likely to be found on the plains and in the Seronera area. The cheetah, which is sometimes mistaken for a leopard, is a more lightly built animal and has dark 'tear marks' which almost join the corners of the eyes to the mouth. Female cheetahs are always solitary but males sometimes form groups of two or three. There is no marked birth season and up to six are born in a secluded nest site. At six weeks old they start to accompany their mother and remain with her until 15 months old. During this time young cheetahs rely on their mother for food while they develop hunting skills.

Cheetahs are specialized predators relying on a concealed approach to prey followed by a swift chase. Their hunting consists of getting as near the prey as possible before the final rush. Although chases can reach 100 kph they cannot be sustained beyond 300 meters because cheetahs over-heat quickly. Cheetahs rely primarily on eyesight and do not hunt at night. Unlike lions they do not hunt cooperatively and they lose many kills to these larger predators as well as to spotted hyenas. In the Serengeti cheetahs prey primarily on Tompson's gazelles. During the wet season they follow the gazelles onto the short grass-plains, but in the dry season they move to the Seronera and Wandamu Rivers where cheetah density is highest in Africa. The cheetah's diet is also supplemented by hares, antelopes, such as impala and Grant's gazelles, as well as the young of wildebeest and topi.

Each cheetah has its own individual pattern of spots on its face and chest, and banding on its tail. You should be able to tell whether your second cheetah sighting is the same animal as your first. If the cheetah is lying down, make a quick sketch of the prominent spots of the cheek. If the animal is walking, a record of the width of the black and white bands on the tail will do just as well. Compare these records next time you see a cheetah.

During the dry season vast numbers of Yellow-Throated Sandgrouse congregate on the short-grass plains. They are very noticeable as you are driving alone the road, because they frequently wait until the last minute before springing into the air and flying. They usually sit in pairs, the male being distinguished by the black-brown on the foreneck. Sandgrouse feed on seeds and shoots, and are often seen congregating in huge numbers at available watering places.

The Ratel or honey badger will sometimes be seen on the short-grass plains, usually in the morning or evening. It has coarse grey fur on the back separated from the black underparts by a white lateral stripe. Ratels feed on wild bee grubs, eggs and young of birds, small mammals and reptiles. They are extremely courageous creatures, attacking fearlessly anything, however large, that appears to threaten them and have been known to bite the wheel of a car when approached too closely.

In the Serengeti there is an interesting partnership between the ratel and the black-throated honey-guide. As its name suggests the bird leads the ratel to a bee hive, and perches nearby while the hive is broken open, hopping down to feed on the wax of the comb as soon as demolition is completed. The tough skin of the ratel seems to be impervious to bee stings.

An animal closely related to the ratel is the Zorilla or striped polecat Although these animals are usually nocturnal, the black and white stripes and bushy tail, make them easy to identify if seen in the daylight They are very skunk-like in appearance and habits, feeding mainly on small mammals, reptiles and ground nesting birds.

The large bird with grayish-brown plumage, is the Kori Bustard. The male bird, which at 12 kgs weighs considerably more than the female, is the heaviest bird in Africa which can fly. However it is mainly seen on the ground. The male has a spectacular display during the breeding season when white plumage around the neck and tail are raised as the male calls.

Special Thanks to Thomson Safaris and Tanzania National Parks for contributing Tanzanian information.

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