Cattle are increasingly replacing wild ungulates on the world’s rangelands and prairies, but new research from Utah State University scientists suggests that cows and zebras may have similar effects on grasslands.
Zebras, elephants and giraffes have grazed the savannas of Kenya’s Laikipia Plateau for millions of years, but since 1995 these large herbivores have been fenced out of eighteen plots at the Mpala Research Center. Cows, which are relative newcomers on the landscape, are grazed on some of the ten-acre plots but not others. Scientists from around the world come here to study the effects of these grazing manipulations on the ecosystem.
“So, if these wildlife species were to go up to a buffet, some of them would want to eat iceberg lettuce, some would want to eat spinach, some would want to eat arugula, whereas cattle you can be pretty sure, because it’s just one species, they’re going to always want to eat the arugula.”
Dr. Kari Veblen, an assistant professor in Utah State University’s Department of Wildland Resources and Ecology Center, recently published a paper in the journal Ecological Applications describing the effects of cattle and wild herbivores on the plant communities in the Mpala plots over 14 years. They found surprisingly similar effects of cows and native wild herbivores, such as zebras. No surprise, the tastier species of grass decreased and the less palatable ones increased in the grazed plots. But what was surprising was that the overall plant community was similar whether it was being grazed by moderately stocked cattle or the native ungulate community.
“So there are two important caveats. One is that you might still expect cattle to have really unique effects on a plant community because they typically occur at higher densities than wildlife do. The other is that we also looked at individual plant species and how they responded, and it turns out that a given plant species tends to respond more strongly to either cattle or wildlife.”
The key seems to be stocking cattle at moderate densities. It’s also important to note that the team did not look at the effects on woody plants and trees, which are dramatically altered by large herbivores like elephants and giraffes, which both browse and topple trees.
