Zoo keepers in Switzerland have given a behind-the-scenes glimpse into the mind bug-ling menu demands of hundreds of animals in their rainforest enclosure.

11,000 square metre (118,400 square feet) enclosure – at Zurich Zoo – has no borders and any of the 500 animals from 40 different species can wander anywhere.

But while it is great for the animals, keepers at the Masoala Rainforest have a dizzying list of diets and allergies they need to follow to keep the inmates healthy.

Video footage – obtained by Newsflash from the zoo – shows one keeper working flat out as she delivers specialist treats to different species.

Chameleons are seen getting stuck into a special release of grasshoppers with their amazingly accurate tongues.

And red ruffed lemurs are seen tucking into specially chosen fruit that is low on vitamin C because their bodies cannot process it.

Keepers are even seen hand-feeding birds who normally eat on the wing by throwing insects into the air from a sky-high platform.

In a statement from 16th August obtained by Newsflash, experts at the zoo said: “Feeding all those different animals appropriately is a special challenge due to the natural and unrestrained way they are being kept here.”

They explained: “While some species depend on high intakes of vitamin C, other animals would suffer from such consumption.”

The keepers went on: “The red ruffed lemur would binge on sweet fruit all day.

“However, lots of sugar is bad for its teeth, and it struggles to digest vitamin C.

“The red ruffed lemur only exists on the peninsular of Masoala northeast of Madagascar. Deforestation puts the species at risk.

“At Zurich Zoo, there are seven male and six female red ruffed lemurs. The female peers are in charge of things here.”

The Rodrigues flying fox – an endangered bat species – prefers very ripe fruit, say keepers.

They explained: “They separate the fruit pulp into tiny bits in their mouths, spit out the fibres to suck just the juice.

“In contrast to other animals, the Rodrigues flying depends on lots of vitamin C.”

Their special diet is put into bulbous barrels hoisted up in the air to keep the red ruffed lemurs away, keeper Daniela Kollmuss explained.

And to ensure a healthy diet for their Madagascar ibises, keepers hide their food in special narrow holes that only their long, pointed bills fit into.

Zurich Zoo’s Masoala Rainforest enclosure opened in June 2003.