Initial surveillance using high-tech thermal imaging equipment, baited motion detection cameras and DNA testing of scat and fur had not yet confirmed the presence of any wallaby, but experienced response contractors with two specially-trained wallaby-tracking dogs had arrived last week to undertake additional surveillance.
Mr McElrea said that with several species of wallaby long present in other parts of New Zealand, the potential Far North sightings were being taken seriously. "If indeed a wallaby or wallabies are here, the most likely scenario is a deliberate, and illegal, liberation from either the central North Island or Kawau Island," he added.
Wallaby were famously introduced to New Zealand almost 150 years ago when Sir George Grey released them on Kawau.
Regional council chairman Bill Shepherd said he was pleased the sightings were being taken seriously.
"This is a potentially a very serious incursion, and a proactive multi-agency response now significantly reduces the risk of another pest potentially becoming established in Northland," he said.
Mr McElrea understood the witness had seen a wallaby on at least two separate occasions at Waimamaku over recent months, but had not initially appreciated the potential significance.
The council only became aware of the situation in mid-April, after news of the sightings reached another Hokianga local, who realised the seriousness of a potential incursion and alerted the Department of Conservation.
Locals in the search area had been supportive of the multi-agency efforts, he said, adding that the situation served as a reminder of the need to report any suspicious animal, fish or plant as soon as practicable to the regional council's biosecurity team (on 0800 002-004).
One of the specialists brought in to search is Te Puke man Guus Knopers, who runs Bay of Plenty-based company K9 Detection, with his 8-year-old german short-haired pointer Lotte, who has been specifically trained to track wallabies.
Mr Knopers says it took about 12 months' training for Lotte to gain her special DoC certification.
They were doing a lot of wallaby tracking in the Waikato and Bay of Plenty.
Mr McElrea said the regional council was footing the roughly $10,000 bill for the initial response, but if a wallaby incursion was confirmed a more extensive eradication campaign would be needed.