A zoo in England has stopped feeding bananas to its monkeys, saying the fruit is too unhealthy.

The Paignton Zoo Environmental Park in Devon says bananas are much higher in sugar than the fruit the monkeys would eat in the wild.

"People usually try to improve their diet by eating more fruit," the zoo's head of conservation and advocacy, Amy Plowman, said in a statement.

"But fruit cultivated for humans is much higher in sugar and much lower in protein and fibre 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."

She says bananas can have negative health effects for monkeys.

"Compared to the food they would eat in the wild, bananas are much more energy dense – they have lots of calories - and contain much more sugar that's bad for their teeth and can lead to diabetes and similar conditions," she said.

"It can also cause gastrointestinal problems as their stomachs are mostly adapted to eating fibrous foods with very low digestibility."

A typical monkey diet now features lots of green leafy vegetables, smaller amounts of other vegetables and as much leafy branches as the monkeys will eat.

Matthew Webb, the zoo's senior keeper of mammals, says the new diet is having positive results.

"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," he said.

"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."

Animals do still get bananas if they are unwell and the keepers need to make sure they take medication.

"Putting it in a piece of banana works really well, as it's such a treat now," Ms Plowman said.

ABC/BBC