Otago Regional Council environmental monitoring and operations director Scott MacLean said the dry conditions made for a good breeding season for rabbits.
‘‘The years where you get heavy rain over the summer often drowns some very young rabbits in the burrows,'' Mr MacLean said.
That would not have happened this year.
Areas with high numbers at the moment included parts of the Upper Clutha basin.
The spike in rabbit numbers would add to the stress farmers were already facing because of the dry weather.
‘‘Controlling rabbits comes at a cost and it is a very difficult season for a lot of people.''
The hot, dry summer did make it possible to carry out summer oat poisoning in some areas. Rabbits looked for other food sources when vegetation was hit by the lack of rain.
‘‘It does open another opportunity to get on top of them.''
Federated Farmers Otago president Phil Hunt, who farms in the Upper Clutha, said rabbits thrived when it was dry.
‘‘It would be fair to say we have got more of a problem,'' Mr Hunt said.
Increased rabbits resulted in more environmental damage and could ruin productive land.
‘‘They eat the plants to such a low level that they actually kill them.''
Farmers and other landowners in rabbit-prone areas would have to carry out more rabbit control, come autumn.
‘‘It's not just a problem for farmers.''
