Most of the dogs Mr Knopers, the owner of K9s for Conservation, takes on board are those dumped at the pound or the SPCA.
Once he has trained them, they frequently get taken on as detector dogs for the Department of Conservation, Ministry of Agriculture and Forestry and the Ministry for Primary Industries.
"Dogs are proven to be more efficient at doing this kind of work than humans," he said. "These dogs get a second chance."
The dogs he chooses are those with drive that like to hunt for the ball and are old enough to be past the excitable puppy stage, but young enough to still be trained.