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."