Elephants Have A Very Human Way Of Eating Dinner

In the same way you might hate to eat the same food for every meal, every day, elephants have been found to vary their diets from day to day.

Researchers investigated the eating habits of individual elephants in two groups in Kenya and found that these elephants varied their diets not only based on food availability but seemingly on mood, according to a study published in the journal Royal Society Open Science on July 4.

One of the most surprising results, Tyler Kartzinel, an assistant professor of environmental studies, and of ecology, evolution and organismal biology at Brown University, and co-author of the paper, told Newsweek, is that elephants' diets "may depend on who they are or where they are in their life."

"We tracked individuals from one family that were all very sensitive to the changing seasons, eating fresh grasses after it rained and switching to trees when it was dry. But on any given day, they would almost always select very similar diets, given what kinds of plants were available.

"The one standout exception in this family was a 21-year-old female named Matisse who was the only adult member of the family who was not nursing a calf during the study period—she tended to feed more individualistically. By contrast, members of another family were much more likely to feed individualistically regardless of the season."

Elephants are generalist herbivores that eat a huge variety of trees, shrubs, grasses, and other plant species, often foraging in their family groups.

"In this population, our research shows that each individual often uses 50-100 plant species on a daily basis—although they need such huge quantities of food to support their bulk that they usually focus on the 10-15 species of trees and grasses that are most abundant and help them fill up fastest," Kartzinel said.

The researchers figured out the eating habits of the elephants by sequencing the plant DNA found in their dung.

"This forensic method is called dietary DNA metabarcoding, and it enables us to precisely identify the plant species eaten. In collaboration with the non-profit Save the Elephants, our team GPS-tracked individual elephants, following them to collect fresh dung as often as practical," Kartzinel said. "The study's lead author, Brian Gill, sequenced plant DNA from the dung and matched the resulting sequences to a database of known plant species."

This method allowed the researchers to determine what broad category of plant the elephants had eaten, but couldn't discern precise species.

The reason for the elephant's varied diets appears to be a mixture between food availability and personal preference. It has previously been shown that elephants generally switch between eating fresh grasses during the rainy season to eating trees during drier weather, but now, it appears each elephant has its own taste in food, just like us.

"Elephants are so big that they have no choice but to fill their bellies with huge amounts of the most common plants in their environment," Kartzinel said. "These plants may be lacking in some vital nutrients that the elephants need or they may be loaded with anti-herbivore chemicals that the plant makes to defend itself from elephants.

"So elephants may benefit from seeking out other, often rarer plants in order to mix it up if these plants act like a nutritional supplement on top of their stable diet or if these plants help dilute out harmful chemicals that might otherwise overwhelm the elephants if they didn't. Elephants probably have to balance both of these possibilities, which would explain why they are often seen to seasonally diversify their diets."

The authors suggest this may be the reason elephants are able to forage in groups rather than going alone to avoid competition for food; they don't all eat the same thing at the same time, leaving plenty to go around. However, they didn't test for these social effects statistically, so this is more of a suggestion for now.

They hope these findings might help to inform conservation biologists about how best to protect elephants and provide the correct range of plants for the group, and also prevent elephants from stealing human crops, which is a major source of inter-species conflict with humans.

"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," Kartzinel said in a statement.

"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."

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