The explosion in the rat population in the South Island has prompted the Government to commit an extra $20.6 million for a second set of 'Battle for our Birds' 1080 aerial poison drops, especially in Kahurangi and South Westland this winter and spring.

A Greymouth pest controller says he is having to deal with double the number of rats around the district compared to two years ago.

Murray Piner, of Piner Pest Control, attributes the explosion in rat numbers to a big beech 'mast' or fruiting since late last year.

"The rats have got food and are breeding. People are getting quite a problem in their houses with rats and mice. Both rodents are a problem," Mr Piner said.


"From the year previous to last year they have literally doubled."

As a sign of the size of the problem this year, he was being called to a lot of houses he had not been to before.

"Some say they have never had a problem with rats."

The problem seemed to be worse in urban areas, while in country areas farmers especially were used to rats and bought poison bait to control them.

"In the urban areas ... it hasn't happened before and the rats are coming in on people."

Rodents were more of an issue for houses next to creeks, or on the edge of the bush. The problem was exacerbated by the cold and wet conditions which "moves them out of the bush to look for warmer places".

He believed it would continue to get worse over the next month as the rodents were forced inside by the cold.

Mr Piner advised anyone who spotted rats around the property to not leave food scraps lying around. "That's a very important part, or rubbish where rats can get to it."

A rat that is scavenging and comes across food scraps in rubbish bags, will "come back and bring his whole family with him".

Another "clean, healthy way" of dealing with the problem was to set traps, but he said it was important to keep children away.

- Greymouth Star