It is not clear how well a rabbit-poisoning programme on the grounds of Dunstan Hospital is working.
The Southern District Health Board introduced rabbit control measures at the Clyde hospital in November after rabbit holes and droppings were found on the grounds.
SDHB facilities and property general manager Paul Pugh said the fortnightly poison-baiting programme using pindone rabbit pellets would continue until March and be followed by a monthly baiting plan.
It was difficult to know how effective the bait stations had been at this stage because of the unusually high rainfall over the summer, which meant grass was plentiful, and rabbits preferred to eat grass than pellets, he said.
"Usually, in Central Otago, dry summer conditions cause the grass to brown and die back, which would more readily prompt the rabbits to consider eating the pellets."
About 20 rabbit carcasses were removed from hospital grounds before Christmas.
As rabbits mostly returned to their burrows after ingesting the pellets, the total number of rabbits eradicated could not be established, Pugh said.
"We will continue with the programme, and also to monitor and review the problem and our response to it."