Dunedin has had a bumper year for rats, which the Dunedin City Council's contractor says is the worst in the past seven years.
Dave McPhee, who deals with rodents throughout the Town Belt, and in reserves across the city, said the rats were being targeted throughout the year as part of the council's rat control programme.
The most prevalent was the ship rat.
"There are huge numbers, and we're trying to keep on top of them."
Apart from being an unwelcome guest in reserves, the rats ate the eggs of native birds.
There were bait stations, locked to keep children and dogs out, throughout the city's bush reserves, and the bait was being "cleaned out" by the rats.
"It's the highest uptake I've ever seen," Mr McPhee said.
The situation was not just affecting Dunedin, with recent work he had done in Mason Bay, on Stewart Island, showing the same problem there.
He was unsure what had caused the extra numbers, though a drier winter could have been a factor.
"The reason for it in the Town Belt area, I really don't know," Mr McPhee said.
"They seem to have bred, and I've never seen anything like it. We can see them running around in the bush."
Despite the recent high numbers, he said the council's control programme, which had been running for the last six or seven years, had helped the bird population, with birds like tuis, waxeyes and bellbirds making "a huge comeback" in the bush.
- The ship rat has a pointed muzzle and large eyes and ears.
- The tail is longer than the combined length of the head and body.
- Found across New Zealand, the rodents are implicated in the decline or extinction of many New Zealand land birds, and have decimated populations of insects such as large weevils and giant wetas.
- Ship rats are highly fertile - one pair can produce a population of 3000 in a year.
