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Waiting for their daughter to finish work in the nature park's cafe, they were walking on a public track directly outside the confines of the ecosanctuary, a couple of weeks ago.
Mrs Tokona saw something moving in the grass beside the track, and at first mistook it for a rat.
When the couple realised it was a tuatara, Mr Tokona's instinct was to try to catch it.
He briefly made contact and it scuttled away; he was concerned he might hurt the animal if he tried again.
The Karitane-based couple marked the spot on the track with stones, and alerted the ecosanctuary.
Conservation manager Elton Smith caught the pregnant female and returned her to safety.
Outside, she would not have survived long - Mrs Tokona had seen a stoat just minutes before the tuatara.
Ecosanctuary general manager Chris Baillie said it was likely the tuatara was swept through water gates that open in high rainfall.
Tuatara can hold their breath for up to one hour.
It was also remotely possible it had scaled the ecosanctuary's fence.
The tuatara was one of 87 introduced to the sanctuary in 2012 to form the southernmost wild population in more than a century.
The female had since laid her egg, as had many of the other wild tuatara. None had hatched yet.
Mrs Baillie said the wild tuatara were rarely glimpsed by the public.
Visiting the ecosanctuary yesterday, the Tokonas handled a tuatara for the first time, when they were introduced to one of a captive pair.
The wild tuatara are tagged for identification, but are not electronically monitored.