Why do Wildebeest Migrate?
Each year, more than one million wildebeest begin a journey that is nature’s most phenomenal wildlife spectacle. Such a vast and uninterrupted movement across East Africa is not mindless roaming, but rather the expression of an instinctive survival strategy that has been determined by climate, the growth of grasses, and the natural environment.
Wildebeest migration is often called the heartbeat of the African savannah, and it nourishes ecosystems, predators, and landscapes along the way. To know the reason behind wildebeest migration, we need first to analyse their biological aspects, the environment, and the strong natural powers that propel them onward.
The search for food: Grass is the primary motivation
Food is the main reason why wildebeests migrate. Being grazers, wildebeests depend mainly on short, highly nutritious grasses. They cannot, for example, feed on leaves all year round like giraffes, which are browsers, as they need fresh grass that is rich in protein and low in fiber. Such grass only grows after seasonal rains.
There are two main rainy seasons in East Africa, and rainfall is not evenly spread throughout the region. Since rains fall in different parts of the year in different areas, fresh grass grows in different locations. A wildebeest has to follow the moving green wave to stay alive. When the grass in one area gets dry or overgrazed, they have to move elsewhere to find a better feeding spot.
This is the reason wildebeest go back and forth from the southern plains of Serengeti National Park to the northern grasslands of Maasai Mara National Reserve. Their migration pattern is closely connected to the changes in rainfall; thus, they can always have the best pasture to feed on all year round.
Water availability shapes the route
Water is another critical factor, besides grass, for the wildebeest. When they are hot and dry, they must drink at least once or twice a day. If the rivers and waterholes dry up, large herds can’t stay in one place without risking dehydration.
The route of migration is along the water points or to the areas where the water is expected to come with the rains. During the dry season, rivers like the Mara River serve as major crossing points.
Even though these crossings are very risky because of the strong currents and crocodiles, they cannot be avoided. If the herds did not cross, they would be trapped in areas with very little food and water.
By their willingness to face extreme danger, the herds show how important water access is to their survival. It also explains why migration is not just an option but a necessity.
Survival Through Numbers: Safety in the Herd
Migrations also allow animals to escape from predators. A herd of wildebeest keeps on growing up to hundreds of thousands of individuals. The unit moves together, thus providing safety in numbers and therefore making it less likely that a single individual will be a victim of predators such as lions, hyenas, and cheetahs.
When wildebeests go on their migration, their predators prefer going after them almost as if it were a moving predator-prey system across the savannah. While many wildebeest are sacrificed to predators during the journey, the herd overall gains. Especially the calves, since their survival rate is much higher if they are in the middle of thousands of adults.
Moreover, the constant movement makes it hard for predators to overhunt a particular area.
For example, if the wildebeests were to stay in one place throughout the year, the pressure from predators would be much higher and possibly lead to the extinction of both species.
Reproduction and Calving Cycles
One of the main reasons wildebeest migrate is to reproduce successfully. Most wildebeest births take place in a very short period of time, that is, within a few weeks. Calving is synchronized and timed so that it coincides exactly with the period of peak grass quality.
The purpose of this mass calving is to overwhelm the predators. When hundreds of thousands of calves are born almost simultaneously, predators can’t catch them all. Moreover, the plethora of fresh grass allows nursing mothers to be well-fed and thus to produce milk and regain their strength after giving birth.
After the rains, the southern Serengeti flats are of utmost importance for calving as the volcanic soils there yield very nutritious grass. Once the grass starts to get dry, the herds are forced to move again; thus, the cycle goes on.
Ancient Instincts and Learned Behaviours
Migration of wildebeest is instinctual, but an instinct honed by experience through many generations. Calves trail their mothers across pathways first traversed millennia ago.
While individual wildebeest do not know about climate or geography, their collective behaviour is an amazingly responsive system to changes in the environment.
It is believed that wildebeest can predict coming rain by detecting ocean pressure, by smelling it, or by hearing the thunder. In conjunction with memory and group movement, this permits the herd to change direction and timing with astonishing precision. There is, crucially, no one leader at the head of the migration.
Rather, the movements that make up the animal’s migration are an “emergent property” that results from a vast number of tiny decisions by individuals based on grass quality, water, and herding instinct.
The wildebeest migrates because that’s what they do. Their migration is an extremely vivid example of nature’s harmony, where the migrating species are driven by the need for fresh grass, water, reproductive success, and survival. It is not a matter of choice or curiosity but an instinct, which has been shaped through thousands of years of adaptation to a harsh environment.
