African ranchers often prefer to keep wild grazers like zebras off the grass that fattens their cattle.
But a new study by Kenyan and University of California at Davis researchers shows that grazing by wild animals doesn't always harm, and may sometimes benefit, cattle.
The results are published in this week's issue of the journal Science.
"Although savanna rangelands worldwide are managed on the premise that cattle and wildlife compete for food, there is little scientific information to support this assumption," said Wilfred Odadi, a researcher at the Mpala Research Centre in Kenya and a co-author of the paper.
"When we look at the effect of wildlife on cattle, we find that they sometimes do suppress weight gain by cattle, but also sometimes enhance it," said Truman Young, a plant scientist at UC Davis and lead author of the paper.
"Generally the decision has been to exclude wild animals, but we're saying that things are not that simple," Young said.
"The finding that wildlife has a positive effect on cattle growth and production during times of plenty adds new insight into the role that facilitation plays in natural communities," said Saran Twombly, program director in the National Science Foundation's Division of Environmental Biology, which funded the research.
"Results from this study also speak directly to the critical importance of biodiversity in maintaining natural ecosystems," Twombly said.
The researchers enclosed 10-acre plots of savanna rangeland with fences to exclude wild animals--principally zebras.
Then they weighed the cattle grazing either with or without wild grazers to measure how much weight they put on at different times of the year, which is the bottom-line for ranchers.
Odadi and colleagues found that during the dry season, grazing by wild animals reduced weight gain by cattle, but in the wet season, cattle actually put on more weight when
|Contact: Cheryl Dybas|
National Science Foundation