Spin-Cycle: The Great Migration

It’s been called a Natural Wonder of the modern world, immortalized by dozens of nature shows (and one well-known Disney movie), and it consistently tops safari-goers’ lists of “must-see” events during their trips: it’s the Great Migration of the wildebeest (and zebras).

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But there’s more to this cycle than most travelers know; the continuous movement of millions of grazers through the plains of the Serengeti is driven by a multitude of factors, any one of which can stall (or jump-start) the process in unpredictable ways.

For wildebeest, the start of the new year means new life: all across the plains of the southern Serengeti, millions of animals start calving (depending on a host of other factors, calving can occur anytime between January and March).

Wildebeest with calves
Photo by Thomson Safaris guest, Victor Nemeth, MD

By the time the calving is over, right around 500,000 wobbly newborns will join the herds (just thank your lucky stars you didn’t have to deal with all the baby showers). Luckily, their home turf in the south is relatively flat, with wide-open vistas in most every direction, a fact that greatly increases their odds of survival (the herd, on high alert because of the babies, can more easily spot predators and gather in large groups, a time-honored defense tactic).

Wildebeest as far as the eye can see!
Photo taken by Thomson Safaris guest, Chris Donovan

In the Serengeti, as in song, April showers bring May flowers…or at least spring grasses. Heavy rains bring the Serengeti to lush, green life and start the river systems flowing. Well-fed wildebeest are able to produce gallons of nutritious milk for their young, who grow quickly.

Of course if those rains come early, the cycle might move on to its next stage more quickly; if they come late, the wildebeest may linger longer over their month-long meals. The herd’s schedule at this time, and throughout the cycle, is heavily dependent on the weather.

Unfortunately for the ladies, wildebeest fellas like their females with a little meat on their bones…and they like them a lot. After just a month of indulgence, the bulls become restless, chasing each other—and most all the adult females—around in order to assert their right to rut (the eminently charming name given to the wildebeest’s annual mating).

Wildebeest bulls spar
Photo: Andy Biggs

Which means that by the time your average maternity leave ends, female wildebeest are pregnant again, for the next 8-9 months. There are downsides to being so attractive, no?

Throughout the summer, the herds spread out on their way north (love ‘em and leave ‘em seems to be a wildebeest motto), converging on the Mara river system in the northern Serengeti as the lands become drier, and food sources grow ever more scarce.

By September, months of heat and dieting have left the wildebeest herds on edge (would YOU want to be stuck with that many underfed pregnant women?). Hunger and boredom (or, you know, instinct) sets them on edge. Occasionally a crazed rebel will decide he can’t TAKE IT ANYMORE and starts sprinting across the river.

Their impulse control withered by hunger, anywhere from a handful of wildebeest to hundreds follow the nonconformist across.

Great Migration river crossing
Photo taken by Thomson Safaris guest, Patti Sandoval

…Then back. Then across again. In fact, until the light rains get going in November (enough so that water pools have filled significantly; wildebeest’s sensitive palates can’t tolerate plebeian PH levels), drawing them back to the south, they might criss-cross the river several times a day (perhaps just to break up the monotony), or they may not cross for several days on end (we are held in the grip of l’ennui). These small-group crossings (because with a total herd size around 2 million, even 1000 animals crossing is a drop in the bucket) can occur at any given point along the massive Mara river system. Because of this, they’re not only unpredictable (who knows when a wildebeest might just…SNAP), it’s rare to catch them.

But once the rain falls, grazing and alternative water sources allow the wildebeest to finally get a little change of scenery with a nice trip down South.

…and then the wildebeest migration starts to resemble another wildlife (film) favorite: Groundhog’s Day.

“Traffic jam” in Tanzania
Photo taken by Thomson Safaris guest, Ann Dickerson