Say aah – orang-utan opens wide as teeth checked at Dudley Zoo

It ended up taking four keepers at Dudley Zoo to carry out the task – bribing the two-year-old ape named Sprout with her favourite grape treats.

Eventually they managed to persuade her to show off her pearly whites, and she does so proudly in front of her mother Jazz.

The job in hand was to count her teeth as part of an international research project at the Black Country zoo. The zoo's upper primates section leader Pat Stevens said: "We were asked to take part in the British and Irish Association of Zoos and Aquariums (BIAZA) captive orang utan tooth emergence project.

"Unlike dad Jorong, who willingly opens his mouth on command, Sprout wasn't too keen on the idea and had to bribed with her favourite grape treats.

"It was a real team effort to count Sprout's teeth," Pat said.

"It took four keepers, each counting a different section of her mouth at the same time, as well as taking a lot of grapes to coax her."

Sprout has 22 teeth in total, so has quite a few more to come through until she has the full set of 32, the same as humans, Pat Stevens added.

She said: "As soon as we finished counting she opened her mouth as wide as she could – she really can be a cheeky monkey."

Sprout was born at the zoo, based on Castle Hill, two years ago. After birth, the baby orangutan was kept in a quiet private chamber away from members of the public, until mother Jazz was ready to show her off to visitors.

Before the orangutan was born, her mother stopped eating onions, Dudley Zoo staff noticed.

Staff at the zoo say Sprout has developed well over the past two years, becoming more and more independent.

But she will remain dependent on Jazz until she is at least six years of age.