African herbivores share space but not diet

Grazing cow near elephants

Cattle graze along with wild herbivores, including elephants, on the plains of Kenya, but they tend to have different plants on their menus, a new study finds.

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There’s a good reason why so many people want to go on an African safari — savannas in Kenya and other countries are home to plenty of large, photogenic animals, including elephants, giraffes and lions. Who wouldn’t want to see those creatures up close?

But there’s something a bit quirky about those savannas. They can be home to 10 or even 25 different species of herbivores that all seem to be eating the same narrow set of plants. How do they manage to coexist?

The answer to that question is in the animals’ poop.

Tyler Kartzinel of Princeton University and colleagues studied herbivorous mammals living at the Mpala Research Centre in Kenya. At the center, native wildlife live in 200 square kilometers of unfenced landscape, where they mingle with herds of livestock raised by local people. During the 2013 wet season (June to July), the researchers collected 292 fresh fecal samples from seven herbivorous species — elephants, Grevy’s zebras, plains zebras, buffalo, impala, dik-diks and domestic cattle — living within the center’s boundaries. They then analyzed the DNA of the plant matter in the feces to determine what each animal was eating. The results were published June 1 in the Proceedings of the National Academy of Sciences.

“Diet composition was similar within species and strongly divergent across species,” the researchers write. The team had predicted that bigger species would have more diverse diets, but there was no evidence of that. And while there was overlap in which plants each animal ate — they all consumed a mix of grasses, forbs and trees — they ate very different amounts of the different types of plants.  

The two zebra species, cattle and buffalo belong to a category of plant-eaters called grazers. These animals eat vegetation down to ground level. All munched heavily on the most abundant species, Pennisetum stramineum, and tended to eat the same amount of grass. But they each ate a different mix of the other grasses, even the two zebra species. 

Dik-diks are browsers — animals that eat leaves, bark and stems — and they ate yet a different set of plants. Elephants and impalas, which don’t fall neatly into the grazer or browser category, had their own menus.

The finding that herbivores don’t necessarily have a lot of dietary overlap could help in environmental management, the team notes. “Wildlife and livestock overlap in rangelands worldwide, and resource competition between them (both real and perceived) is a major source of human-wildlife conflict,” they write. Similar studies could help to identify the real areas of conflict and help to guide management efforts.

Sarah Zielinski is the Editor, Print at Science News Explores. She has a B.A. in biology from Cornell University and an M.A. in journalism from New York University. She writes about ecology, plants and animals.

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