London ( CNN ) -- Monkeys and bananas . It 's as natural a pairing as squirrels and nuts or movies and popcorn . Not any more , says one zoo in southwest England . Paignton Zoo in Devon is grabbing bananas out of its monkeys ' hands , giving them leafy veggies and sprouts instead . This is no monkey-business diet fad , though . The zoo says the high calorie and sugar content of bananas grown for human consumption -- which are sweeter than those found in the wild -- are bad for the monkeys ' health and can rot their teeth . `` Bananas grown for human consumption are full of sugar and calories , and bear no relation to fruit grown organically , '' said zoo spokesman Philip Knowling . `` Life in the wild is hard work and in a zoo you can sometimes look after the animals too well and it is n't good for their health . '' Thicker , better fur . Humans can continue gobbling up their bananas , just keep them away from monkeys . `` Sweet and juicy bananas are good for humans but not for monkeys , '' Knowling said . `` Animal nutrition has become a problem . Bananas and monkeys is a bit of a cliche , but they 're not a good combination . '' The zoo has not been able to find a supplier for the kind of wild-grown bananas that would be more suitable for the monkeys , he said . So , it decided it was time to put them back on the shelf . The zoo has seen `` definite changes '' in the monkey 's behavior since the bananas were slowly withdrawn from their diet , Knowling said . `` We 've noticed a net improvement in their coat and their fur is thicker and better . Some of the smaller monkeys are less aggressive , '' he said . Thailand 's annual 'monkey buffet ' Diabetes risk . According to the zoo 's head of conservation , Amy Plowman , the bananas ' high sugar content could cause the monkeys to develop diabetes or similar conditions . `` It can also cause gastrointestinal problems as their stomachs are mostly adapted to eating fibrous foods with very low digestibility , '' she said . Zoos are getting smarter in the way they feed their captive animals . Rather than throw in ready chopped and prepared food , many now try to make the animals `` work '' for their calories by searching for scattered foodstuffs or doing puzzles to release treats . This is just the next step , Plowman said . Knowling said there was no obvious sign that the monkeys were missing the fruit . In fact , they could well be happier without the extra sugar . `` 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 , '' said Matthew Webb , senior head keeper of mammals . `` Reducing the sugar in their diets has calmed them down and made their groups more settled . '' Iran claims 2nd launch of monkey into space and back .
Paignton Zoo in England takes banana out of its monkeys ' diet . Zoo says the high sugar content of banana grown for food is bad for them . Since bananas were introduced , the monkeys ' coats and tempers have improved .