The new rabbit haemorrhagic disease virus released in Canterbury and Otago seems to be taking effect.
Environment Canterbury and the Otago Regional Council made controlled releases of the RHDV1 K5 strain in autumn to help reduce the wild rabbit population.
ECan biosecurity regional leader Graham Sullivan said the council was unable to say how many rabbits had been or would be killed.
''However, early results suggest we can expect the reduction to be within the originally anticipated range of up to 40%,'' he said.
''The virus was released at 92 sites across Canterbury in March-April. The Eastern Mackenzie Basin has the largest rabbit numbers in Canterbury.