PROVIDENCE, R.I. [Brown University] — Elephants eat plants. That’s common knowledge to biologists and animal-loving schoolchildren alike. Yet figuring out exactly what kind of plants the iconic herbivores eat is more complicated.
A new study from a global team that included Brown conservation biologists used innovative methods to efficiently and precisely analyze the dietary habits of two groups of elephants in Kenya, down to the specific types of plants eaten by which animals in the group. Their findings on the habits of individual elephants help answer important questions about the foraging behaviors of groups, and aid biologists in understanding the conservation approaches that best keep elephants not only sated but satisfied.
The study was published in the journal Royal Society Open Science.
“It’s really important for conservationists to keep in mind that when animals don’t get enough of the foods that they need, they may survive — but they may not prosper,” said study author Tyler Kartzinel, an assistant professor of environmental studies and of ecology, evolution and organismal biology at Brown. “By better understanding what each individual eats, we can better manage iconic species like elephants, rhinos and bison to ensure their populations can grow in sustainable ways.”
One of the main tools that the scientists used to conduct their study is called DNA metabarcoding, a cutting-edge genetic technique that allows researchers to identify the composition of biological samples by matching the extracted DNA fragments representing an elephant’s food to a library of plant DNA barcodes.
Brown has been developing applications for this technology, said Kartzinel, and bringing together researchers from molecular biology and the computational side to solve problems faced by conservationists in the field.
This is the first use of DNA metabarcoding to answer a long-term question about social foraging ecology, which is how members of a social group — such as a family — decide what foods to eat, Kartzinel said.
“When I talk to non-ecologists, they are stunned to learn that we have never really had a clear picture of what all of these charismatic large mammals actually eat in nature,” Kartzinel said. “The reason is that these animals are difficult and dangerous to observe from up-close, they move long distances, they feed at night and in thick bush and a lot of the plants they feed on are quite small.”
Not only are the elephants hard to monitor, but their food can be nearly impossible to identify by eye, even for an expert botanist, according to Kartzinel, who has conducted field research in Kenya.
Understanding an elephant’s favorite foods
The research group compared the new genetic technique to a method called stable isotope analysis, which involves a chemical analysis of animal hair. Two of the study authors, George Wittemyer at Colorado State University and Thure Cerling at the University of Utah, had previously shown that elephants switch from eating fresh grasses when it rains to eating trees during the long dry season. While this advanced study by allowing researchers to identify broad-scale dietary patterns, they still couldn’t discern the different types of plants in the elephant’s diet.
The scientists had saved fecal samples that had been collected in partnership with the non-profit organization Save the Elephants when Wittemyer and Cerling were conducting the stable isotopes analyses almost 20 years ago. Study author Brian Gill, then a Brown post-doctoral associate, determined that the samples were still usable even after many years in storage.