Ecosanctuary general manager Chris Baillie said the stoat was believed to be shy of trapping mechanisms, so staff were building a ''run through trap''.
In the trap, the mechanism was hidden in the ground and the stoat would become trapped, after believing it could run through the device.
A similar trap in the Kapiti Island Nature Reserve had caught a stoat, which had been loose on the island for four months.
The trap would include bedding straw used by a female stoat, which the ecosanctuary had been given.
She expected the ''strong'' scent in the straw to attract a male stoat, and possibly a female stoat.
Staff have been trying to catch the stoat since footprints were found in the snow inside the ecosanctuary in late June.
As a precaution, juvenile kiwi were evacuated to islands in Lakes Manapouri and Te Anau.
The sex of the stoat was unknown.
Since the hunt began, the elusive stoat had not eaten any of the baits in the ecosanctuary, including eggs and rabbit meat.
However, a new bait, two live mice, had been laid.
The mice were in a trap in an area of the ecosanctuary which posed no danger to the ecosanctuary if the mice escaped, she said.
The staff had found no further sign the stoat was in the ecosanctuary.
''The snow on Sunday wasn't thick enough for us to see prints clearly.''
Although staff had no ''hard evidence'' the stoat had killed any native animals in the ecosanctuary, Ms Baillie was confident it had.
''You can be sure it has eaten native birds, because that's what we have in here - we have no mice and rats - and it's inevitably eating things.''
She was confident the adult kiwis and takahe could defend themselves against the stoat.
''The tuatara have been checked and they seem to be doing OK.''
If the stoat was not caught in another fortnight, a dog trained to hunt stoats would return to join the search.
Once the stoat was caught, an ''audit'' would be done to reveal the extent of the damage, she said.
