It’s February, and we all know what that means: it’s peak calving season for wildebeest living in East Africa. As we speak, thousands of wildebeest are being born, all at the same time.
Also known as gnu, wildebeests are large antelopes living in Africa. They have a boxy, cow-like head, a horse-like body, and the long, thin legs of a gazelle. Wildebeest are one of the most common herbivores found in Africa and generally prefer to be in vast, open areas.
The name “wildebeest” comes from the Dutch settlers moving inland from the African coast in the 1700s. It literally means “wild beast,” a nod to the fact that wildebeests look like large species of cattle or ox.
Black and blue
There are two species of wildebeest: black wildebeest (Connochaetes gnou) and blue wildebeest (Connochaetes taurinus). Fossils indicate that blue wildebeest evolved in Africa at least 2.5 million years ago, with black wildebeest then diverging into a separate species 1.5 million years ago.
The blue wildebeest is more common than black wildebeest and is found across southern and eastern Africa. They live in a wide range of habitats, from dense woodland to open floodplains. Blue wildebeest often have a blueish sheen to their fur and have horns that curve out to the side before curving up. These animals are gregarious and will form large herds, sometimes with other animal species like zebras.
In contrast to blue wildebeest, black wildebeest tend to live in drier, more open areas. Black wildebeest are also the shorter of the two wildebeest species, only growing to almost 4 feet (120 centimeters) at the shoulder compared to the blue wildebeest’s nearly 5 feet (150 centimeters). However, black wildebeests have larger horns than blue wildebeests, and their horns curve forward and down before curing up. In addition to their brown to blackish fur, black wildebeest have a creamy-colored tail and light-colored mane. Black wildebeest live primarily in South Africa and are more solitary than blue wildebeest. They are also much less migratory, and instead, males usually defend a territory that females will pass through.
The Great Migration
The blue wildebeest, not the black, take part in the so-called Great Migration. Over one million blue wildebeest engage in a yearly, circular migratory journey through the Mara and Serengeti ecosystems in Tanzania and Kenya, following rainfall in search of fresh water and new grass to eat. The Great Migration is the largest herd movement of animals on the planet, and columns of wildebeest can be seen from space.
While the Great Migration is continuous, let’s start our discussion with the calving season. Wildebeest are seasonal breeders, and 90% of calves are born within a three-week period in late January and early February. Nearly 8,000 calves are born every day while the herd occupies the eastern edge of the Serengeti. The grass here is particularly nutritious, providing a valuable food source for mothers to raise their newborn calves.
The herd eventually moves northward toward fresh grass in the central Serengeti. Mating season occurs in late May, with the males fighting for access to females. By June, the dry season has started and wildebeest have begun gathering in the Serengeti’s Western Corridor. This is where the large river crossings start, with the herd first having to cross the crocodile-infested Grumeti River. July brings the herd to the even riskier Mara River crossing, where many animals are either eaten or drowned.
But by August, most of the herd has crossed the Mara River and is spread throughout the Masai Mara’s northern region. They spend their September and October gradually moving eastward before crossing the Mara River again as they move southward. They continue moving south and east through November and December, eventually ending up back at the calving grounds where their journey started.
Note: not all blue wildebeest are migratory. There are populations of sedentary blue wildebeest throughout their range. Sedentary males will defend a small territory that herds of breeding females will pass through from time to time.
Helping the Savanna
Migratory blue wildebeests play a crucial role in keeping the savanna healthy. For starters, wildebeest are an essential food source for predators. The calving season is a particularly easy time for hunters due to the sheer number of wildebeest and vulnerable calves. River crossings are also dangerous, as predators wait on the banks for stragglers and crocodiles snap at crossing individuals.
Wildebeest bodies also play a vital role in the health of the savanna. Drowning at river crossings is common, as thousands of wildebeest try to cross a river at the same time. Add in strong currents from recent rain, and you have a recipe for animals getting swept off their feet. Research has found that an average of 6,250 wildebeest die at river crossings each year, equal to the mass of 10 blue whales. While crocodiles and scavengers may eat some of the bodies, they can only eat so much. Instead, much of the over 2 million pounds of wildebeest meat slowly rot, providing vital nutrients for the ecosystem. Wildebeest bones become covered with a biofilm, which serves as food for fish. The bones also release phosphorus into the river, slowly decomposing over seven years.
And, of course, wildebeests play a vital role in fertilizing and spreading seeds throughout the savanna with their dung.
Not bad for an ungainly-looking creature!
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