The great migration is endless and ageless. It is a continuous circuit punctuated with climaxes like the mass wildebeest calving in the southern Serengeti, and the great crossing of the crocodile infested Mara river. It is a fluid transfer of energy from sun, to rains, to grasses, to grazers, to predators, and finally back to the lands. It is a cycle of motion, which supports the circle of life, and is one of the greatest natural spectacles on earth.
Cycles of Sun, Wind, Rain and Wildebeest
At the beginning of the year, the warm winds from the Indian Ocean blow inland to the plains, dumping rain. The plains are green with new grass and the herds graze in the southern part of the Serengeti. However, around June as summer starts over South Asia, the winds shift, blowing the rains out west, and the dry season starts in the Serengeti. During this period the herds head northwest towards Lake Victoria where its vast waters are still producing localized rains. The herds concentrate in northern Tanzania during the middle of the year, beginning to arrive in Kenya’s Maasai Mara in August or September. Then around October or November, they start heading south again to their calving grounds in the southern savannah, in expectation of the rains.
Each Circuit is Unique, Each Decision Anarchistic
However, the ebbs and flows of temperatures every year create different micro patterns of wind, guiding the rainfall to the ground along distinctive pathways. Like Sisyphus relentlessly pushing the rock up hill, the great herds of grazers constantly chase the thunderclouds on the horizon, in perennial pursuit of the green shoots of grass on the savannah. They are the ultimate nomads, never settling anywhere, ready to follow the rains everywhere through their yearly 480 km (300 mile) circuit around the Serengeti.
These variations in the weather, mean that no two migrations ever follow the exact same path or timing, and therefore each is unique, having a personality and life of its own. The cycle has no beginning or end, no designated leader or trail. This anarchist tendency and lack of definition allows it to fluidly adapt while constantly staying in motion. The migration is an instinctual urge to find food, always a little further ahead — the grass is always greener on the horizon.
Co-dependence of Grazing Cycles
At least a million wildebeest, 250,000 zebras, 350,000 Thompson’s gazelles (Tommies) participate in the parade. The zebras pioneer the way, delicately snipping the tops off the grass. The wildebeest are never far behind, mowing down the stalks to about an inch off the ground, and the nervous little Tommies prance along at the back, pulling the remaining tidbits from the ground with their elongated snouts.
The feeding habits of these species complement each other as they cycle through the plains. Eating different parts of the grass ensures they are not in competition for the same food, and can all herd together. The zebras can then keep watch through the long tendrils of grass for prowling predators, while the wildebeest keep their nose to the wind, and the Tommies constantly twitch their ears detecting the slightest slither through the waving blades of grass.
The Interlocking Circles of Life
All along the way, predators lie in wait. The herds are a windfall of opportunity, which they wait for all year, and use to train their young to hunt. The herd’s epic travel means they are always in unfamiliar lands, always in another predator’s hunting ground, never quite knowing which tree, or termite mound may cloak long fangs and sharp claws. Leopards, lions, and crocodiles attack the herds at will, and the hyenas and cheetahs pick off the small and weak.
An estimated 750,000 animals die during the migration each year, but many are actually killed by the herd itself, trampled in frantic unorganized motion. Therefore, the herd brings both safety and peril. It is insulating and erratic, preserving life, and a likely cause of death. However, both in life and death, the herds give back to the plains that nourish them.
The herds do not just graze the grass; they actually also help catalyze its growth. Animals leave a fertilizing trail of saliva, dung, blood and bones across the plains. The herds leave an estimated 3,620 tons of dung per day, which the dung beetles diligently roll and bury with their eggs. This ensures the arrival of the next rains will spur healthy regrowth. This is a great circle of life from the rains that grow the grass, to the grazers that feed on it, providing food for the predators and fertilizer for the earth.
Cycles Must Sync with Circles
In 2015 the northern rains in Kenya came late and so did the migration, and then the plains flooded in an alarmingly extreme weather pattern. With climate change, the rains are becoming more erratic, which makes the migration less predictable and the life that depends on it more precarious. Further, the Tanzanian government has been talking about a highway through the Serengeti, as well as a heated oil pipeline from Uganda, a railroad and an international airport, all of which have the potential of significantly disrupting the migration.
For all of the complexities of the migration, it seems fairly simple to observe that if the weather patterns the animals follow shift, or human encroachment impedes the herds’ pursuit of the thunderclouds on the horizon, this cycle of motion may fall out of sync. So these grazers do not have the green grass they need when they are calving, and the predators do not have the herds pass through when their offspring need to learn to hunt.
It is important that cycles of weather continue to support this circuit of motion, which allows the complex circle of life to persist in the savannah. For without it, not even the savannah itself would survive. Currently, the systems seem balanced yet threatened, and we are likely to see shifts in the future, which affect this famous ecosystem. This could be a travesty for the species of the savannah, the governments and local communities that earn revenues from it, and the travelers that traverse the world to witness this incredible spectacle.
Author’s Note: For those planning a trip to see the great migration, Herd Tracker can help you understand where the herds currently are located.