A zoo where animals, including a dangerous monkey, escaped from their enclosures on four occasions has denied staffing levels are an issue there.
Lemurs got through a gap in the roof netting at Hampshire's Marwell Zoo and were recaptured, the BBC has learned.
But a female macaque scaled a live electric fence and was shot with tranquiliser darts, between 18 and 20 July this year.
The case is being investigated, but one worker claims staff levels are too low.
'Keepers missing'
James Cretney, chief executive of Marwell Wildlife, said: "It has never happened before, the electric fence was still on and an investigation is underway into exactly how the macaque escaped.
"We have to practise escape procedures regularly, it is not a question of keeper error or staffing levels.
"The incident was dealt with quickly and very professionally and the public were not at risk."
The female Sulawesi-crested macaque was tranquilised by a veterinarian with with a gun.
But a worker at Marwell, who did not want to be named, has told BBC News he had grave concerns about public safety.
"For the people at the site it is scary," he said.
"It is not the situation where they are looking to blame the zoo but by the same merit, if they had been aware that so many of the keepers were missing and the animals were still being let out into their outdoor enclosures perhaps that would have been different.
"If you have to fit another five animals in your day as well as look after your normal grouping there is going to be some mistakes made.
"[The macaques'] teeth are an inch-long and they are very territorial, so there would have been a risk to babies and toddlers in push chairs.
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