Rat numbers in Wakatipu areas hit by 1080 in late August have plummeted, the Department of Conservation says.
Yesterday, DOC said rat numbers had fallen to undetectable levels after a steady rise over winter.
"In the Dart Valley the number of monitoring traps detecting rats is now at just 1 per cent. This figure was 6 per cent in May, 13 per cent in July and without the 1080 operation the figure would have climbed even further."
However, in nearby areas not treated with 1080, the rat tracking percentage was now a high 30 per cent.
DOC covered nearly 20,000 hectares of conservation land across the Dart, Routeburn and Caples valleys in the hope of decimating the rat and stoat populations and protecting native birds.