The journey for the key players in the Great Migration, the roughly two million wildebeest, starts in the south of the Serengeti, with the birth of half a million calves between January and March. A favourite season for many of the seasoned Serengeti guides: the air during these months is full of new life and action. Read all about Africa’s biggest wildlife event on this page.
The 800 kilometer trek of the immense wildebeest herd is the largest mammal migration on earth. The timing of the migration coincides with greening of nutritious grasses on the short-grass plains during the wet season. These areas are safer because predators can be easily spotted making it an ideal place for calving. However, the plains dry and the wildebeest are forced to move in search of greener pastures in the western corridor. The northern extension of the ecosystem has the highest rainfall, but the grasses are least nutritious. This is the dry season retreat for the wildebeest, at least until the south becomes green again. The result is a clockwise movement from the south, west, north, and back to the south.
What makes a million wildebeest get up and move at once?
What is the sense that triggers them to muster the energy to begin a 1000-kilometre trek—to somehow know that it’s the right thing to do?
It’s mid March in the northern Tanzania, and thousands of animals are happily milling on the rolling plains of the Serengeti. The female wildebeest have just dropped their calves in a beautiful display of new life, as the youngsters stumble and stagger to their feet and are up and running within minutes. There’s still plenty of food to go around, and life must seem pretty idyllic for the wildebeest.
And yet, one, or two, or maybe a few hundred wildebeest sense something in the air.
For some reason, a few animals decide to start moving. They just get up and go, and the rest begins to follow.
Just like that: the largest terrestrial mammal movement of animals on earth has begun; the great wildebeest migration.
It is a trek, a round trip, of some 1000 kilometres, over two countries (Tanzania and Kenya), across plains where predators—lion, cheetah and leopard—wait to pick off them off, over hills, and through rivers with crocodiles waiting; battling disease, starvation, thirst and fatigue; with around 250 000 animals perishing along the way.
Despite all this turmoil ahead, without fail, they go.
Why do they do it?
Why, when most wildebeest in Africa are non-migratory, do the animals of the Mara/Serengeti ecosystems risk it all in one mad trip?
No scientist or naturalist has yet been able to answer this question conclusively. But there are some theories.
Studies using aerial photography show a remarkable level of organisation in the structure of the wildebeest herds as they start moving. The groups display a wavy front that snakes out like the head of a swarm. This amazing structure cannot be apparent to each individual wildebeest, which means that there is some degree of decision making that is happening between the animals. Is there some sort of leadership being displayed; maybe a form of communication we don’t yet know about?
Some scientists believe that the wildebeest are motivated by the chemistry of the grass. The herds are attracted to higher levels of phosphorus and nitrogen, which changes in response to the rains. So perhaps the wildebeest are merely following their taste.
It might simply be instinct. Fossil evidence suggests that wildebeest have been roaming the plains of East Africa for over one million years. In the same way their body tells them to run when a lion appears out of the grass, maybe the instinct to migrate has been coded into the DNA of the animals over many years of evolution.
Perhaps they just know—and so they just go.
Whatever the reason, over 1.5 million animals begin a journey that will undoubtedly cause death to many of their own, but will also bring life to many more animals as they follow the rains in search of green nutrient-rich fields that will sustain the next generation.
And so they charge onwards.
The Great Migration ?
A better representation of the circle of life probably cannot be found anywhere else in the world. The journey starts in Southern Serengeti when wildebeest calves are being born. Predators like lions and hyenas are constantly hunting for babies, and thousands and thousands of calves are born within a couple weeks of each other – a feast for the eyes of true wildlife enthusiasts.
When the drought comes in May, the herd moves north, to the Masai Mara in Kenya, chomping down the high green grass, quickly followed by the gazelles and zebras. The migration is not without risk: crossing rivers means facing about 3,000 crocodiles, patiently waiting for a kill. Not to mention the famous Serengeti lion population: by far the largest in Africa. Despite the abundance of hoofed meat in this area, life is not easy for these big cats in this unforgiving landscape. But seeing a group of lions collaborating to hunt down a wildebeest is an unforgettable sight.
Then, with the beginning of the short rains in late October, the migration makes its way back into the Serengeti. By December, the herds trek past Seronera – a small settlement in central Serengeti where the official Serengeti Visitors’ Centre is located – to return to their calving grounds again, and the circle is complete.
The Great Migration in detail
When planning your Serengeti safari you probably want to include seeing the Great Migration. So how do you ensure to be there when it happens? The long and short of it is that you can’t. It is important to realize that the decision of when to visit the Serengeti always involves an element of risk. We have detailed the Great Migration below, and this is what usually happens, but keep in mind that there are no guarantees.
The annual migration of two million ungulates, wildebeest but also enormous groups of zebra and Thomson’s gazelle, Grant’s gazelle and eland, through Serengeti National Park is the greatest wildlife spectacle of its type in Africa, and perhaps the world. Although variations occur from year to year, the Serengeti migration follows a reasonably predictable annual cycle, dictated by local rainfall patterns. The Great Migration cycle breaks up into the following periods:
We can find the main calving grounds in the area southeast of Seronera: typical Serengeti plains stretch all the way to the Ndutu area near Ngorongoro. Triggering their move to this area are the short rains in November and December. The wildebeest stick around this area until the end of the long rains, end of April, early May. The delightful news is that this section of Serengeti National Park is easily accessible and that in this period the landscape becomes lush. February is usually calving season in the Ndutu area and the southeastern plains: the very best time to visit this area. As wildebeest, zebra and other ungulates are so many, and give birth to so many calves, the spectacle works as a magnet for predators. As early as March or April the herd may move again in search of greener pastures. Seeing the actual migration in this period is more difficult, but chances are that you will encounter very large herds on the move.
This is the period that the wildebeest, after having feasted on the short green grasses of the southeastern Serengeti and after having giving birth to their offspring, start getting ready for their 800 kilometer long trek. The actual starting date may be anytime between late April and early June. This is the time to you may have the privilege to see one of the greatest natural phenomena in the world: more than a million marching animals in a column up to 40 kilometers long. During the migration, the herd will move towards the Western Corridor, where they will face the first major obstacle: crossing the Grumeti River. Many animals don’t survive the crossing as they are being awaited by the area’s population of oversized crocodiles ready to feast. The herd may congregate on the southern bank of the river and stay there for up to two weeks before crossing the river.
When the Grumeti River obstacle has been taken, the herd moves further north and starts crossing the next big hurdle, the Mara River, in July or August. The Mara River crossing is where so many iconic Great Migration photos have been taken. After this crossing the herd flocks to the northwest plains and Masai Mara National Reserve in Kenya. The August – September period is considered being a bad time to visit Serengeti National Park and see the Great Migration as the herd moves into the Masai Mara in Kenya. However, migration patterns show that about half of the herd stays on the Tanzanian side, in the Mara Serengeti area. In this period, smaller herds of wildebeest (well consider small… herds may count up to between 500 and thousands of individuals) frequently cross the Mara River, back and forth, for no apparent reason. This is an excellent time to stay at one of the Serengeti Mara camps.
Crossing the Mara River northbound means that, at one point, the herd needs to cross the river one more time before commencing the trek back in a southerly direction. This usually happens in October, but sometimes earlier. In this period the herd will cross the northern plains and Lobo area. This section of Serengeti National Park is little-visited, so if you are looking to see the migration in relative quietness, this would be the time. The wildebeest return to the short- grass plains and calving ground around Ndutu in late November. And from here, the Great Migration starts all over again.
As mentioned earlier, the timings outlined on this page concern guidelines as exceptions occur frequently. In November 2013, the wildebeest already started trekking back to the southern Serengeti short-grass plains when suddenly it started raining north of the Mara River. Nature is as nature does and the herd turned around, back into the Masai Mara in Kenya. The herd stayed there for about three weeks before resuming their southbound journey. A year later, in 2014, freak rains in the southern Serengeti caused much of the herd to remain behind and not make the northbound journey towards the Western Corridor up to July.
When to visit?
It is a matter of choice whether you would like to plan your Serengeti safari around the Great Migration. We have mentioned earlier that the Serengeti is a year-round destination as it covers a vast area and offers unparalleled wildlife viewing. Chances that you will be at the exact spot of the Great Migration herd crossing a river (either at the Grumeti or Mara River) are very slim. Also, the timing of herd movements cannot be guaranteed. However, if you choose the right part of the Serengeti: the southeast and Ndutu from December through to May, the Western Corridor from May to July, the Serengeti Mara area from July trough to October, and the northern Serengeti and Lobo area in October and November, large herds of wildebeest and their entourage should be easily located.