Image caption The Saki monkey is one of a number of species that can survive almost entirely on fruit

Researchers say that some monkeys in South and Central America eat as many as 50 different species of fruit a day.

A team from the University of East Anglia said that primate size and diet are closely connected.

They found that mid-sized species including Saki monkeys were the biggest fruit consumers.

Larger primates including Woolly Spider monkeys were more likely to eat leaves and foliage, they said.

The research has been published in the journal Oikos.

It is only the larger primates that are able to cope with the higher levels of toxins that are typically found in leaves Dr Joseph Hawes, University of East Anglia

The scientists pulled together data from 290 studies of diets in primates in Central and South America spanning 42 years.

Five a day

They found a clear relationship between animal size and dietary preferences.

Small monkeys such as marmosets and tamarins eat more insects and less fruit.

But as body size increases so does the preference for juicier foods. Species like Saki monkeys can eat between 45 and 50 species of fruit every day, often consuming their "five a day" in a hour of foraging.

Image caption Bigger species eat more leaves as their guts can handle toxins better

Larger animals including Howler monkeys and Woolly Spider monkeys preferred leaves and foliage.

"We found that the diet of medium-sized primates is most likely to be dominated by fruits," said Dr Joseph Hawes, a co-author of the study.

"Smaller monkeys, which have higher metabolic requirements, eat more insects as the provide a high quality source of nutrients and calories," he said.

Rare fruits

And while monkeys are traditionally associated with eating bananas, the researchers found it wasn't the most popular fruit in South and Central America.

Instead, fruits from relatively unknown trees including the Pouteria and Brosimum, were preferred.

As primates get bigger in size, their fondness for fruit wanes while their fancy for foliage increases.

"It is only the larger primates that are able to cope with the higher levels of toxins that are typically found in leaves," explained Dr Hawes.

"They have a more complex gut."

The scientists say their work is important not just as a way of assessing the conservation needs of different species, but in helping them gather data on the richness of plants in tropical forests.

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