Monkeys at Australia's Melbourne Zoo have been put on a banana-free diet because selective breeding of the fruit has made it too sugary, the zoo's head vet told The Sydney Morning Herald. It's not just the monkeys that are being restricted, either. Other animals at the zoo were becoming obese and suffering from rotted teeth, and ultra-sweet fruit was identified as the culprit.

"The issue is, the cultivated fruits have been genetically modified to be much higher in sugar content than their natural, ancestral fruits," head vet Michael Lynch tells the Morning Herald.

Some fruits, like plums, have nearly doubled their soluble sugar content in the last two decades, food scientist Senaka Ranadheera told the Morning Herald. Some wild bananas have large seeds, but the cultivated variety that we eat has been genetically modified to the point that it's unrecognizable from its less-palatable counterpart. In addition, "wild apples are smaller and more bitter than modern cultivated varieties," Ranadheera said. Fruit with a higher sugar content simply tastes better to humans as well as animals.

At Melbourne Zoo, the primates and red pandas have developed quite a sweet tooth. It's not unusual for the animals to eat all of their fruit while leaving other foods untouched. In an attempt to introduce a healthier diet, zookeepers have started feeding the red pandas bits of pear mixed with "panda pellets" containing all the nutrients and minerals they need. Other animals have had their fruit swapped out for leafy greens.

The Australian zoo isn't the first one to take fruit off the menu, though. In England, the Paignton Zoo tracked the health of its monkeys from 2003 to 2010 and ultimately decided to eliminate fruit, bread, eggs, and seeds from the animals' diets. Instead, they are fed foods rich in protein and fiber, including pellets, fresh vegetables, dog biscuits, and cooked brown rice. "Resultant health benefits have been improved dental health and weight loss in some previously overweight individuals," Dr. Amy Plowman at the Whitley Wildlife Conservation Trust wrote in her 2013 research paper.

[h/t Newsweek]