Authorities at Cleveland Metroparks zoo have put Mokolo and Bebac, their two adult gorillas, on a new diet in a bid to get the apes in better shape.
Gone are the starchy, processed food pellets that the pair used to munch on. Instead, the gorillas are scarfing down wheelbarrows full of vegetables, including green beans, dandelion greens and endive.
They're swallowing more than 10 pounds of vegetables a day.
The zookeepers aren't just worried about the gorillas looking their best for visitors. An ultrasound had shown that both of the apes were suffering from heart disease.
"We're beginning to understand we may have a lot of overweight gorillas," said Kristen Lukas, a curator for conservation and science at the zoo and an adjunct assistant professor of biology at Case Western Reserve University. "We've raised our standards and are asking, Are they in the best condition to not only survive but to thrive?"
A year into the diet and the results are encouraging. Each of the massive beasts has shed almost 65 pounds, despite the fact that they're now ingesting twice as many calories a day.
The veggie-heavy diet requires the animals to spend a lot more time eating each day, but they appear to be enjoying it.
"They were a little disappointed at first that their diet was lower in sugar," said Elena Hoellein Less, a Ph.D. student at Case Western. "Just like humans, they really like their sugar."
The new diet in Cleveland has helped get Mokolo and Bebac back to the weight of their counterparts in the wild. It has also helped reduce behavior that gorillas don't normally display in the wild, such as plucking out and eating their own fur.
Zoos in cities including Toronto and Seattle are now testing out the diet.
For researchers like Less, the gorilla health drive continues. "The next step is exercising gorillas in zoos," she said.