Invercargill City Council (ICC) acting group manager community services Pete Thompson said senior living species officer Lindsay Hazley discovered the dead 31-year-old reptile on July 14, during regular maintenance of the tuatarium.
There had been real shock and sadness for staff, and also members of the wider community, he said.
"It’s curious we’ve had some feedback from people who’ve heard and they’ve said, ‘I don’t see tuatara very much but I still feel a sense of ownership and it’s so hard to have heard this’, so people can really appreciate what our staff are going through."
The rat was found in another part of the museum, where damage had been done to the albatross diorama and a line fishing display nearby.
"We don’t know how many rats were involved.
"We have captured a rat that was involved with the collection damage, and we haven’t found any more evidence of rats of either being in the tuatarium or the museum, so it could be the same rat."
The rat, which was caught live, was now in a freezer awaiting a postmortem, Mr Thompson said.
It was thought the rat was likely to have gained access to the enclosure by scaling a two-metre PVC pipe and climbing through an air vent, Mr Thompson said.
It was believed it was the first time a predator had infiltrated the tuatarium which was designed to be predator proof.
Remaining tuatara were removed while steps were taken to re-proof the enclosure and had since been returned.
Further rat and mouse traps were bought and chemical-free pest control options were being explored for the galleries near the tuatarium.
Mr Thompson said council’s parks and recreation team would now include the museum and its surrounds in its pest management programme
"We have been cautious with the use of poison, and this is only being used in areas where there is no risk to the tuatara. We’re aware there have been deaths in other parts of the country where insects have eaten poison, and those insects have then been eaten by tuatara."
Iwi and the Department of Conservation have been notified of the tuatara’s death.
He could not confirm if the dead tuatara was the offspring of beloved tuatara couple Mildred and Henry.
