After a plea from a father and son who became trapped in a zoo while taking photos, Sydney zoo authorities have since round up more than 45 primates.

Photo: AFP

Three of the creatures were taken to a special research and conservation unit, where they will be assessed to assess if they should be sent to an accredited facility, Dr Robyn Bigelow, curator of captive animal husbandry at Taronga Zoo, told AAP.

"Obviously we would need to ascertain their mood and well-being before making a decision about the future of this species," she said.

"Then the final decision to release or not to release depends on both the merits of a release proposal and also the fact of what the animals know about their personal freedom."

Two cats and a dragon were also taken away from the enclosure after one slipped through a gap in the fence and led police to her.

"The snake was standing there on all fours with its hands on its head and it was as quiet as could be, no funny business," Dr Bigelow said.

The cats have had freedom and have never been released into the wild, she said.

Another giraffe was also moved away from the enclosure, where he had been sleeping for three months.

The family who found their way into the enclosure and the zoo authorities did not wish to comment, AAP reported.

Earlier on Thursday morning a father and son paid a visit to Taronga and were taken back in time.

An eagle-eyed father had spotted an escaped monkey in the enclosure.

He and his son walked right up to it and then heard the monkey scratch at the enclosure's fence before motioning at it to get on the ground, ABC reported.