THE GREAT MIGRATION – SERENGETI ECOSYSTEM AND NATIONAL PARK
SERENGETI AND THE GREAT MIGRATION
The Serengeti is a vast ecosystem in east-central Africa. It spans 12,000 square miles (30,000 square kilometers), giving rise to its name, which is derived from the Maasai language and means “endless plains.” The region hosts the largest mammal migration in the world and is a popular destination for African safaris.
Altitudes in the Serengeti range from 920 meters to 1,850 meters, The usually warm and dry climate is interrupted by two rainy seasons — March to May, and a shorter season in October and November. The Serengeti landscape can be divided into two regions defined by their dominant vegetation — woodland and grassland. Woodlands, which are grassy areas dotted with trees, can then be broken down further by their dominant trees —Acacia woodlands and Terminalia woodlands. Grasslands include riverine, plains and derived grasslands (or those grasslands that are only there because of repeated fires).
The expansiveness of the Serengeti is interrupted by Ol Doinyo Lengai, the only active volcano in the area and the only volcano that still ejects carbonatite lavas that turn white when exposed to air. When it rains, the ash turns into a calcium-rich material that is as hard as cement.
The southeastern area lies in the shadow of the Ngorongoro highlands and is composed of short grass treeless plains, as this area does get rain. Some 43 miles (70 km) west, acacia woodlands rise suddenly and extend west to Lake Victoria and north to the Loita Plains.
The landscape is dotted with a number of granite and gneiss outcroppings known as kopjes, which are large rocky formations that are the result of volcanic activity. The Simba Kopje (Lion Kopje) is a popular tourist stop.
Serengeti – Meru Kopje lions.
Much of the beauty is attributed to its sweeping vistas and dramatic natural features that extend over 60,000 square kilometers. TheSerengeti has more than 2 million herbivores and thousands of predators. Blue Wildebeests, gazelles, zebras and buffalos are the animals most commonly found in the region. Apart from wildebeest, the Serengeti plains are also home to lions, hyenas, rhinos, leopards, cheetahs, jackals, servals, aardwolves, and wild dogs. We saw and photographed all of those, including elephants, buffalos, giraffes, hippos, crocodiles, warthogs, baboons, velvet monkeys, zebras, gazelles, elands, kudus, impalas, nyalas, waterbucks, bushbucks, duikers, mongoose, honey badgers, ostriches, herons, flamingos, buzzards, vultures and dozens of species of birds.
- THE GREATER SERENGETI ECOSYSTEM.
The Serengeti National Park itself covers about 15,000km² of mostly flat or gently rolling grasslands, interspersed with the occasional rock outcrops, or kopjes. But this is just the centre of a whole ecosystem which covers more than double that area, and includes Grumeti Reserve, Ikorongo Game Reserve, Loliondo Controlled Area, Maswa Game Reserve, part of the Ngorongoro Conservation Area and also Kenya’s relatively small Maasai Mara Game Reserve. This combined area is often referred to as the Greater Serengeti area, or the Serengeti-Mara ecosystem.
Vast short-grass plains cover the south of Serengeti National Park, stretching into the north of Ngorongoro Conservation Area, the south-west Loliondo and Maswa Game Reserve. Occasionally there are small kopjes which, like the forests around Lake Ndutu, harbour good populations of resident game. However, around these oases of permanent wildlife, the majority of this area is flat and open. It’s alive with grazing wildebeest from around late-November to April, but can be very empty for the rest of the year.
THE SERONERA AREA
In the heart of the national park, just to the north of the short-grass plains, Seronera has all the best features of the Serengeti and also, sadly, its worst. Scenically, it’s a lovely area – with open plains, occasional kopjes and lines of hills to add interest. The resident game here is phenomenal, with high densities of relaxed leopards, cheetah and lion. These live off the resident herbivores, as well as the migrating game. The migration passes through here in April/May, but Seronera is within reach of both the Southern Plains and the Western Corridor – so from about November to June, it can be used as a base to see the migration. Seronera’s big drawback is that it is always busy;
Stretching to the west, almost to Lake Victoria, the Serengeti narrows into what’s known as the Western Corridor. The key feature of this area is the two rivers, the Grumeti and the Mbalageti, which run almost parallel, each supporting a band of most, evergreen riparian forest. This area sustains a very good permanent game population, including plenty of zebra and wildebeest, all the predators and forest ‘specialists’ like colobus monkeys. The birdlife is particularly varied. The migration passes through between about May and July – pausing to gather momentum before crossing the crocodile-rich waters of the Grumeti River, into the Grumeti Reserve
Stretching from Seronera for about 100km north, to the Kenyan border, the northern Serengeti is gently rolling country, broken by small rivers and occasional hills and kopjes. There are good permanent populations of wildlife in several areas here, including the very beautiful Lobo Kopje.
The further you go north, the fewer vehicles you see. Even when the migration is here, between about August and October, you can still enjoy spectacular crossings of the Mara River. A particularly stunning are is the wild Lamai Wedge – the area of land between the Mara River and the Kenya Border – which includes the picturesque Wogakuria Kopjie, and a beautiful series of game-rich valleys and plains. This is the only area of the national park where off-road driving is acceptable.
Singita Grumeti Reserves covers almost 1,500km² of private reserves which run along the north side of the Western Corridor. Within this are three, very different luxury lodges. All offer unrivalled exclusivity for watching the migration as it journeys north, and recycle all of their profits into local conservation and community development initiatives.
West of the Serengeti National Park, between the Ngorongoro Conservation Area and the Kenyan border, lies Loliondo game Controlled Area – an area belonging to the Maasai tribes that live there. The western side of this, beside the park, is very much part of the Serengeti’s ecosystem; it has much resident game and the migration passes through here as well.
- THE BIRTH OF MIGRATION.
Most people ask where the migration begins. Surely there must be a start and a finish? But there is no real beginning and end of the wildebeest’s journey. Its life is an endless pilgrimage, a constant search for food and water. The only beginning is here, at the moment of birth.
The moment is so carefully synchronized that eighty percent of pregnant cows drop their calves within a few weeks of each other – usually between late January and mid-march. Almost all cows over three years old produce a calf. In recent years the peak has been less pronounced – with such vast numbers involved, it is perhaps more difficult to synchronize the rut so perfectly.
A wildebeest nursing her baby
Among such enormous number of animals it is all easy for the calf to become separated from its mother. Predators and cars sometimes cause the herd to panic, scattering wildebeests in very direction. Calves bleat when they are lost, and it is thought that a cow –given time – learns to recognize the sound of her calf as well as its smell. Orphans wonder through the herd for days, desperately trying to re-find their mothers. But no cow wildebeests will accept the calf for another, even if she has recently lost her own calf and still has abundant milk with which to suckle an orphan. Consequently, these calves pass from cow to cow, each of whom lowers her head to smell them before nudging them on their way again. Some calves are undeterred, following for several kilometers, in the footsteps of a cow and her calf. Even bulls receive tentative advances from lost calves, who soon find themselves rebuked for their error with a rough sweep of the male’s horns. Just occasionally, the seemingly impossible happens and a calf find itself re-united to its mother. But many never do!The marked season of peak birth ensures that young calves are unavailable to predators for much of the year – they are all vulnerable at the same time, and in the same part of their range: predators are glutted by the sheer volume of calves. And therein lies the individual’s best chance for survival. Those born ‘out of season’ are invariably taken out by predators. A calf protection lies in its ability to gain coordination faster than any other ungulate, in being constantly on the move, and in seeking the anonymity of the herd. But many still die before their first year’s journey has ever begun victims of under nutrition, diseases and predation.
Orphans crossing the plains, finding brief comfort in the presence of a fellow creature
Spotted hyenas are by far the most numerous of all the Serengeti’s larger predators. More than three thousand of these formidable creatures spend the wet season on the plains, carefully tracking the movements of the wildebeest as they wonder across the grasslands.Sometimes two orphans will race across the plains towards each other, finding brief comfort in the presence of a fellow creature. But they do not consort for long before rushing off again in search of something more closely resembling the size of their mother – even if not of the shape. Too young you have benefited from the cumulative wisdom of the herd, calves blunder towards hyenas already fat from the day of feasting, or trot blithely into the fatal embrace of lions.
Depicted as scavengers, hyenas are actually skillful hunters
Hyena hunts mainly under cover of darkness, though they are great opportunists, responding quickly, to the presence of vulnerable prey animals.
Their methods are those of coarser, relying on the speed and dogged endurance. When hunting in groups, hyenas are capable of killing adult wildebeests and zebra. Even a single hyena sometimes pulls down a full grown wildebeest. If it does, other hyenas soon arrive and together they tear their victim apart.
A more subtle kind of protection against predators, in particular against hyenas, is the time of the day, when most calves are born. Some are born at Night while shrouded in the darkness. But the majority of births occur around the middle of the morning, even at the midday. By this time, most hyenas are safely out of sight, seeking the shade provided by shallow erosion terraces or lying belly deep in mud wallows, and the lions are sprawled among the cool granite rocks of the nearest kopje. Calves born in mid-morning have the rest of the day to gain strength before predators rouse themselves to hunt again.
- MONTH BY MONTH: THE SERENGETI WILDEBEEST MIGRATION
The short rains begin around early November. A little after this, in late November and December, the herds of the wildebeest migration arrive on the short-grass plains of the Serengeti. These are south and east of Seronera, around Ndutu and include the north of the Ngorongoro Conservation Area. Dispersed across these plains, wildebeest and zebra are everywhere – feeding on the fresh, nutritious grasses. They stay here through January, February and March, with most wildebeest calves born in a short window around February. Gradually they spread west across these plains, then around April they start their great migration north.
By May the Serengeti’s wildebeest all seem to be moving north, migrating to seek fresh grazing and water. The area around Moru Kopjes and west of Seronera is then hectic with a series of moving columns, often containing hundreds of thousands of animals – joined by many zebra, and a scattering of Thomson’s and Grant’s gazelles.
Some of the migration then head due north of Seronera, but most are usually further west. Around June the wildebeest migration is often halted on the south side of the Grumeti River, which has some channels which block or slow their migration north. The wildebeest then congregate there, in the Western Corridor, often building up to a high density before crossing the river. The river here is normally a series of pools and channels, but it’s not continuous – and so whilst they always represent an annual feast for the Grumeti River’s large crocodiles, these aren’t usually quite as spectacular as the crossings of the Mara River, further north.
The wildebeest migration continues moving northwards during July and August, often spreading out across a broad front: some heading through Grumeti Reserve and Ikorongo, others north through the heart of the Serengeti National Park.
September sees the herds spread out across the northern Serengeti, where the Mara River provides the migration with its most serious obstacle. This river gushes through the northern Serengeti from Kenya’s adjacent Maasai Mara Game Reserve. Watching the frantic herds of the wildebeest migration crossing the Mara River can be very spectacular; there are often scenes of great panic and confusion. It’s common to see herds cross the Mara River north on one day, and then back south a few days later.
By October the wildebeest herds are migrating again with more accord: all are heading south, through western Loliondo and the Serengeti National Park’s Lobo area, returning to the green shoots which follow the rains on the short-grass plains of the southern Serengeti in November.
Then the whole Serengeti Wildebeest migration starts again …
- SERENGETI – THE BEGINNING
Africa is unimaginably old. Not far from the original site of the game warden’s house at banagi, a few kilometers out of Seronera, stand some of the oldest rock on earth – two to three billion years. For much of this time there were no animals all. But the ancient land Hs Witnessed the migration, and an array of wild animals the like of which will never be seen again. Spectacular as today herds appear, they are a mere fragment of that golden age of mammals which reached its zenith in Pliocene times, millions of years ago.
Today only the granite kopjes stand as a reminder of the ancient land buried beneath
Each morning as the rising sun warms the rugged flanks of thr Gol mountains, hundred of pairs of Rupell’s griffon vultures preen and squabble the high rocky cliffs of their breeding colonies. The warming rays breathe life into the thin mountain air, creating buoyant , energy-saving thermals for the birds to fly on. First one, then another, then dozens of vultures spread their giant wings and lift off into the blue to begin their daily pilgrimage over the plains. Soaring and gliding, effortlessly moving from one up current to another, the vultures search for carrion. Further and further they fly each day, pursuing the herds across the plain and through the woodlands.
Averaging fifthly kilometers per hour, these vultures must sometimes travel 160 km in a day to find sufficient food for themselves and their chicks. Before nigh-time settles over the land, many of the vultures return to their nests. Crops bulging with meat, clustering in tight feathered groups to listen to the sounds of darkness: a lion menacing a roar, the errie whooping of hyenas, the rasping cough of a solitary leopard.
Only a far ranging vulture can claim to know the secrets of wildebeest’s migration. Only thry know how far the herds travel, and where to find the vast armies from one day to the next. To solve the riddle of the migration’s whereabouts you must fly.
When the first photographic census of the wildebeest population was completed in 1961., it revealed the figure of 263,362 wildebeests, nearly three times the 99,481 estimates by the Grzimeks in 1958. Subsequent counts have chatted five folds increase in the population.
The primary reason for this dramatic increase in the migratory population is thought to be the eradication of rinderpest, a highly contagious viral disease of ruminants. Rindepest is kind of bovine measles, known throughout Europe as far as biblical times, having being introduced to Africa by cattle brought in during the colonial period. The results proved catastrophic and the ensuing cattle plague virtually wiped out Maasai livestock as well as devastating the wild herds of buffalo and wildebeests- species which are particularly susceptible to the diseases.
Over the next seven years , rinderpest become endemic in east Africa, periodically ravaging the Serengeti herds. The highest mortality was among calves, particularly during the second half of their first year, when immunity conferred on them , their mother’s milk have been lost. But once released form the effects of rinderpest and increase in dry season rainfall during 1979’s, the Serengeti wildebeests and buffalo’s population exploded.
- LIFE ON THE PLAINS
For all its ability to stand within five minutes of birth and to out distance a short winded lioness, a wildebeests calf will always be vulnerable on the Serengeti plains to the speed and endurance of a coursing predator such as a wild dog. Its only hope of survival against these formidable hunters lies in passing unnoticed, in being only one amongst thousands of others. But for all their legendary killing efficiency, the impact of the Serengeti wild dog’s population is barely noticed in relation to such enormous number of prey animals.
The African wild god is an enigma. The mere mention of its name is guaranteed to arouse strong emotions. Admired for their sociable nature and the care they lavish on their pups, wild dogs still loathed and despised by many people because they kill their prey by disemboweling. Man has always been quick to judge other species, relegating the dogs to a position of social outcast in the animal world.
Today the wild dogs are among the most endangered predator in Serengeti. There are probably fewer than hundred wild dogs roaming the entire park. The dogs are nomads wondering in search of prey over a large home range of up to thousand square kilometers. For as long as wildebeest are available, the dogs will try to kill them. But when the migration departs in May and June, the wild dogs living in the Serengeti plains survive by hunting the fleet footed Thomson’s gazelles.
Most animals breed during times of plenty, when food is abundant enough to sustain both the adults and the young. This is as true of the wild dogs as it is of the wildebeests. T he majority if the litters are born during the rainy season, between December and May. In years of good rainfall, the wildebeest’s herds mass on the short grass plains during this period and drop their calves, providing easy prey for the dogs during the three months that their pups remain dependent on a den site. At this time of the year the hyenas – wild dog’s major competitor – are often satiated with easy food and their impact is less of a drain on the dog’s resources.
Wild dogs –Hyena’s major competitors
Surprisingly, perhaps the presence of so many wild animals does not damage the plains environment. The wildebeests never stay long enough to do that. As they sweep for one grassland to another they constantly enrich the thin soils, helping to recycle the nutrients before they move on. Everywhere one looks there are dark piles of dung and urine, virtual natural fertilizers. Even as animal clip the grass, growth hormones pass from roots to roots, promoting rapid re-growth. And the saliva of the herbivores acts as stimulants to the grasses. Plants and animals survive in a state of dynamic harmony, allowing both to prosper.
Zebra families are highly coordinated in defense against wild dogs, bunching together and preventing the wild dogs from reaching the vulnerable foals. The stallions fall back, biting and lashing out with their hooves at any dog that dares to try and close in on one of any of their number. None the less they are packs of the wild dogs that has proved to be successfully hunters of zebras. Such packs contain males experienced in the art of immobilizing the struggling zebra by leaping up and grabbing it by the nose and upper lip. Once it has secured in this fashion, other pack members can safely move in and disembowel their prey. But it is a difficult and dangerous pursuit and most wild dogs rely on smaller and easier prey.
- THE LONG MARCH
Groups of lions and leopards look down on the passing herds from their hiding places among the rocks or trees. For as long as the animals continued to poor over the horizon, the predators would have no difficulty in finding food. Hyenas dogged the rutted pathways cut by the wildebeest. Many of these shambling hunters would soon abandon the barren eastern plains and move North West to establish dens at the edge of the woodlands, commuting for days at a time between western corridor and their den sites to prey on the migratory herds during dry season.
The prodigious appetite and protein-rich diets of the predators enable them to endure both feasts and famine. If need be, lions and hyenas can survive for days without food. Not so the wildebeest. They must forever wonder in search for green grass and water. By tomorrow they could be far away, forced to graze for sixteen hours a day to obtain sufficient food – the same amount of time that the predator spends resting.
Lions and leopards are unable to exploit to the full the abundance of the food represented by the migratory herds. With highly dependent young, the cats cannot afford to travel too far afield in their search for prey. They can go off and hunt and then return with a belly full of meat to regurgitate for their young, like the wild dogs. Instead lions and the leopards live as residents within permanent home range. Though some lions venture out n the plains during the wet seasons, most do not follow the herds on the journey north. Those who do are nomadic lions who no longer belong to a pride.
During the dry seasons, the plains are inhospitable place for the larger carnivores – no water, shade, and very few prey animals – just wind and dust. For this reason most lions pride occupy territories in the woodlands, towards which the migration was now headed. But in recently years, the Serengeti lion population has increased – particularly out on the plains. It is thought that a rise in rainfall during the dry season, leading to an increase in the numbers of resident prey species such as warthog and topi, has enabled this to happen.
Hyenas are still more flexible. Though they occupy a particular range which will defend them against other hyena clans, these areas shift markedly in time and space reflecting seasonal changes of their food supply. During dry season the hyenas female are forced to leave their young cubs to go and search for food. This journey invariably takes them to the western corridor where large herds of migratory wildebeests and zebra linger during the early part of the dry season. Having made a kill or while scavenging, hyenas bolt their food, rapidly consuming as many meat as possible. These are the most effective way of competing with other hyenas, and lions that may already be running across the plains to steal the kill.
By the time a females arrives back at her den she may have travelled nearly eight kilometers. By now her udders are bursting with milk. Though they eat meat whenever they can get it, hyena cubs must suck throughout their first year- sometimes until they are nearly 18 months year old, by which time they are virtually full grown. it is only then that they are large enough, and strong enough, to kill for themselves, and to compete among the meal of bodies that quickly accumulates around the fresh carcass.
But even the adaptable hyenas are able to raise cubs and follow the herds later in the dry season. Once the animals moved into the northern extension and on into the mara, the hyenas must rely on resident prey. On the vultures can keep pace with the wildebeests and zebras, can travel 160 km in a day and still return with sufficient food for their young.
The general direction taken by the wildebeests when they first leave the plains mirrors the rainfall gradient, which increases from south east to North West and is strongly influenced by the towering presence of the crater highlands. The short grass areas in the south east lie directly in the rain shadow of the highlands and only receive 500mm of rain annually, almost of all which falls between December and may. Rainfall in areas to north and west is more evenly distributed and may be as much as 1200mm annually, some of which generated during dry season by evaporation from lake Victoria and by thunderstorms produced by grass fires. This dry season rainfall creates a green flush on grazed or burnt areas which is sought after by migratory herds.
Some years the transition between wet and dry seasons is particularly marked. In these circumstances the stage is set for truly dramatic exodus of animals, with hundreds of thousands of wildebeests departing from the woodland at the same time. In fact the term “migration” is most commonly associated with this phrase of the wildebeest’s journey, when the zebra and the Thomson’s gazelles are also on move. But whatever definition on applies to the word ‘the migration’ a change of abode, a seasonal movement – it is misleading to refer only to this one part of journey as ‘the migration’ as a general term to describe the migratory population of wildebeest – not to pin point a particular phase of their year-round journey. The trek from the plains to woodlands is only more spectacular because this is the time when the herds must further and most rapidly to where water and grazing are found. The animals are distancing themselves from the famine of the dry season plains and moving quickly to areas in the north and west where food and water are readily available.
Wildebeest are dependent on water. They must either drink regularly or find grazing with high moisture content. So it’s not surprising to see herds hurrying to the nearest areas, where they can find water as the plains dry out.
Nature has designed the wildebeest to be able to move rapidly and economically over vast distances in search for food- despite their strange looks, they are right size and shape. It takes no more energy for a wildebeest to run a particular distance that it does to walk it. No wonder wildebeests seem in such a hurry – this way they can take advantage. Apart from wildebeest, the Serengeti plains are also home to lions, hyenas, rhinos, leopards, cheetahs, jackals, servals, aardwolves, wild dogs, elephants, buffalos, giraffes, hippos, crocodiles, warthogs, baboons, velvet monkeys, zebras, gazelles, elands, kudus, impalas, nyalas, waterbucks, bushbucks, duikers, mongoose, honey badgers, ostriches, herons, flamingos, buzzards, vultures and dozens of species of birds. They were of the scattered distribution on the green grass, yet still remain within range of water. During the dry season it is race against time. They run to survive.
Nearly every facet of the wildebeest’s behavior seems to have being designed to save time – compressed and abbreviated through necessity. But how else could they accomplish so much so quickly!? They even rut while migrating. And calves gain their feet within minutes of birth so that they may survive in the open and keep up with the ever moving herd.
One of the great mysteries of the wildebeest is the manner in which the animals synchronize the peak in calving, enabling them to bring forth the young at the time most suited to their survival. This is only possible if females ovulate at the same time each year and males restrict their sexual activity to a distinct rut in May and June. The time of mating is critical.
The way in which this complex chain of events is coordinated is unclear. Seasonal changes in a variety of environment factors are known to trigger the production of sex hormones in many animals.
The exact time of the rut is said to be triggered in some way by the lunar cycle, working in conjunction with seasonal changes in other environment influences. But whether the moon’s influences stimulates ovulation in females, or induces rutting behavior in males is unknown. Perhaps it helps to cue both, or perhaps the estrus in females causes the male to rut.
The rut is refreshing contrast for the human observer. Wildebeest society generally does not favor expressions of individuality: survival is enhanced by immersion in the herd. Stand out and a predator is more likely to select you for its next meal. It seems to be a drub life, one spent among countless thousands of other similar beings; a life concerned primarily with obtaining sufficient food while avoiding being eaten. When not advancing in an irrepressible feeding front, wildebeests are surging over the horizon in search of fresh pastures or massing at the water hole to drink. There seems little time for anything else.
In years of good rainfall, both males and females have feasted on steady supply of green forge and are in prime condition to withstand the stress of reproduction with large reserves of energy stored in the form of fat deposits. The bulls look big and impressive, their coats shinning grey with dark fingers of coarse hair streaking their muscular necks and shoulders.
By the time the rut begins in earnest the animals are already moving en masse from the plains to the woodlands. They are now at their most concentrated: males and females are at the same place at the same time, and have no need to seek each other out. This helps to synchronize the bulk sexual activity to within a space of few weeks, ensuring that the next year’s calves are born at the optimal time. By then the herds will have returned to the plains and rain permitting, have access to high quality forage for a month or so before the birth of the calves.
The rutting of wildebeests is closest approximation to organized chaos. So much is happening that you hardly know where to fix your gaze. The noise is deafening. Yet the frantic activity of the bill is far for indiscriminate. To mate they must acquire territory, each year the elder bulls always 3 or 4 years old do battle for temporary possession of a tiny part of turf. Fighting is ritualized as a harmless jousting display designed to select the males most fitted to pass on their genes without unnecessary injuring in their rivals. Territorial bulls constantly perform this ritual with neighboring bulls, galloping out to meet each other, then dropping to their knees, head to head, most of the time they do not make contact. But on occasion they push and spar, horn against horn, the dust rising in clouds around them.
Territorial bulls performing the jousting ritual
This unrelenting activities of the bulls leaves little time for them to feed. They are far too busy displaying and defending their territory, mating with as many receptive females as possible, burning out the energy reserves stored during the previous months spent foraging on the plains. The bachelors mean while are able to maintain their condition and provide a reservoir of fit animals to replace exhausted territory holders. Once ousted from this territory a bull can rejoin a bachelor herd and regain conditions before the energy – sapping dry season reaches its peak.
- SURVIVING THE RIVER
Born in the shallow swamp of among the dwindling forest of the Mau escarpment, the Mara river flows like great artery for fifty kilometers through the reserve. As it courses from north to south, it draws to it a network of tributaries that provide every corner of the reserve with water.
The river is like a chameleon; in places it flows calm and unhurried between steep muddy banks; elsewhere I rushes over great mud chunks of black rock, a deafening white-water torent avoided but its larger residents, hippos and crocodiles, which prefer calmer resting places.
During July or early august, thousands of wildebeest streaming from the hill sides of the northern Serengeti join those already crossing the wide stretch of the Mara river. Certain crossing places become imprinted into the minds of the wildebeests. Sometimes they try and cross the Mara at the suicidal places, plunging over sheer cliffs and drowning in their hundreds beneath an insurmountable wall of mud.
There may be a historical perspective underlying the wildebeest’s choice which is not apparent when viewed on a smaller time scale. Older, more experienced animals probably return to places where they have successfully crossed before, regardless of how many wildebeests died there I previous years.
Certain crossing places attract the largest number of animals because of nature the terrain makes them clearly visible from a long way and creates the setting for a massive exodus of animals across the river. Though the wildebeests and zebra on the surrounding plains and hillsides may not be able to see the river itself, the lie of the land enables them to see other animals heading to that direction. Hippos are continuously eroding new exit point, making trails used by other animals that come to drink. Each animal on in its own way modify the contours of the bank, as does the river itself.
Whatever the factors may be that prompts the herds to cross, and sometimes it’s only a consequence of a build –up animals wanting to drink – nothing deters them once the urge is established. If vehicles or predators disrupt the large crossing at the favorite fording place, wildebeests simply move on to the next, or establish a new one, even thundering through thick forest to reach the river if need be.
The two most commonly used crossing places in this stretch of the river are only few metres apart. One is relatively open, providing good visibility where the river runs rapidly in a spill of white water over black rocks. But the other is quiete different; a cul de sac of open ground, hemmed in between the river and a dense thicket of cover, where the paradise lions often lie in ambush.
The banks are steep on both sides, except for one stretch of mud flats where the river bends sharply. It is here on the flat mud terrace, that the wildebeests gather to drink and cross and when they do, half a dozen crocodiles will already have entered the water in anticipation.
If the buildup of animals trying to cross is too great, scores of wildebeests are trampled or drowned. Others are swept further downstream by the current and become tangled among the branches of the fallen trees. But despite these losses, the majority eventually finds a way through. Somehow they manage to pick their way along the steep rim of mud until a hippo trail or another natural break in the bank releases them.But despite the lions and the crocodiles and the five meter wall of mud facing them, the wildebeests remain undeterred. Each year is the same, a crush of animals desperately treading water on the far side of the bank, searching for a way out. Hundreds of horned heads rear out of the river, eyes burgling white with panic. Usually the first animals are swept back to the shallows unharmed. But by then, others have galloped into the water behind them, forced by the swelling tide of wildebeests trying to enter the cul-de-sac. As more and more seek to cross, the dust rises into the sky like a smoke signal encouraging still other wildebeests to hurry form the plains and follow. The animals seem overtaken by the moment; soon the river turns black with confusion of thousands of grunting, bellowing wildebeest and the water heaves with the bodies.
Many calves become separated from their mothers during the pandemonium of the more difficult crossing. As the bulk of the herd heads off into the distance scores of the cows and calves gallop to and fro, grunting and bleating, mingling with those still trying to cross, sometimes even reentering the river in their efforts to relocate each other.
Some years are worse than others; the height of the river; the place they choose and the number of animals crossing at any one time will determine how many animals die. In a bad year, the Mara claims thousands of victims and the course of the river is made visible from kilometers away by constant swirl of vultures overhead.