Contrary to public perception, bananas are actually bad for monkeys. Nutritionists at Paignton Zoo in the U.K. have banned bananas from their monkeys' diets. Amy Plowman, the zoo's head of conservation and advocacy, told The Telegraph:
People usually try to improve their diet by eating more fruit -- but fruit cultivated for humans is much higher in sugar and much lower in protein and fiber than most wild fruit because we like our fruit to be so sweet and juicy. Giving this fruit to animals is equivalent to giving them cake and chocolate.
In the wild, monkeys like the Sulawesi crested black macaque (one of the species now going without bananas at the zoo) do mostly eat fruit, but their diet relies heavily on figs, not bananas. The crested black macaque does sometimes eat bananas, but not often; it supplements its fig-based diet with other fruits as well as leaves, eggs, insects, and small animals like lizards. And the bananas are unlikely to be the familiar Cavendish; in Indonesia, where the macaque lives, the pisang raja variety is much more common.
Other monkeys may never encounter a banana at all, and won't have be able to make the tropical fruit a large part of their diets. Some, like the black-and-white colobus monkey, are mostly leaf-eaters. Some are even more specific: the golden snub-nosed monkey of Tibet eats mostly lichen. Feeding a banana to a Tibetan lichen-eating monkey is like...well, like feeding Tibetan lichen to us. The monkeys may like bananas, but their digestion systems certainly aren't optimized for them.
So the keepers at Paignton (a well-accredited zoo) decided to use bananas only as treats, or as a sneaky way to get the primates to take medication when necessary. The decision is smart; it's indicative of a need to model a captive animal's diet after its natural diet. Because without a natural diet, animals suffer; they become obese, or lose hair, or get arthritic or sluggish or any of a million other problems that can result from not getting the right blend of nutrients. Animals are no different from us: if we don't have enough citrus, we get scurvy; if we don't have enough calcium, our bones become brittle.
The ban on bananas has had positive effects already:
Senior head keeper of mammals Matthew Webb said: "We have noticed an improvement in the condition of primate coats -- in particular the colour and thickness of the fur of the Sulawesi crested black macaques. Smaller monkeys such as tamarins and marmosets are highly-strung animals and live in tight-knit social groups which can be quite aggressive at times. Reducing the sugar in their diets has calmed them down and made their groups more settled."
ACTION ALERT: Zoos and Aquariums
Hundreds of millions of people visit zoos every year, despite increasing public anxiety about animals in captivity. If you want to make sure you're at least visiting a zoo that makes efforts to be humane, make sure it is on the list of U.S. facilities accredited by the Association of Zoos and Aquariums; internationally accredited facilities are listed hereby the World Association of Zoos and Aquariums. If you want to see whether a facility has any recent USDA violations, you can search this database. You can report a zoo or aquarium to the USDA here. And if you want to become active against having animals in captivity, Peta and Born Free USA offer places to start.