Thousands of cats living in 50 registered feral colonies in and around Tauranga are putting a seemingly never-ending workload on the city's ARRC Wildlife Trust.
Animal Rescue and Rehabilitation Centre (ARRC) manager Sue Mackey said that when they took a proactive approach to stray and unowned cats, they thought the problem would be solved in a year or so.
"Instead it is getting bigger and bigger. We are registering more colonies than we have the facilities to deal with,'' Ms Mackey said.
There were now so many that if people dumped a cat away from prying eyes, the chances were high that there would be a colony nearby, she said.
ARRC is calling for Tauranga to become the first city in New Zealand to require cat owners to register and microchip their pets, together with a limit put on the number of cats per household.
"Nothing we deal with is not the fault of humans in the first instance,'' she said.
ARCC's community cat project, a New Zealand first, has just finished removing more than 80 cats from an Apata property after trapping began in January.
"Neighbours are delighted to see the return of native wildlife to the area. Sadly most of the cats were in very poor health and unsocialised, so they were humanely euthanased.''
Ms Mackey said the Apata site had been a dumping ground for years by people who no longer wanted their cats.
ARCC's success with the Apata colony brings the number of cats removed from feral colonies to more than 700 since the project was launched nearly 18 months ago.
One of ARRC's next priorities is to deal with a huge colony of more than 100 cats at Omanawa. She estimated that about 35 of the 50 colonies needing attention were inside the city boundary, ranging in size from a handful of cats to enormous numbers.
"It's a huge problem,'' she said.
Colonies were quite common in industrial areas, with three or four in Mount Maunganui's industrial area.
Ms Mackey said they were dealing with five or six colonies at a time and so far ARRC had either eliminated or controlled an additional 30 colonies.
Sometimes smaller colonies were left in place provided the cats had been de-sexed, had their ears notched and there was a person keeping an eye on the animals.
The feral colony at Tauranga Racecourse was one of the colonies that had been de-sexed, with the person looking after the cats noticing only one new female needing to be spayed.
Ms Mackey said the trust always tried to rehome kittens and cats that were still tame.
"We rehome everything we can, so long as they are healthy and have a relatively nice nature.''
People shifting house who left the cat behind was the most common call for help from the community, accounting for about a phone call a day.
"People frighten them off and it makes the cat revert to be fairly self-catering. They eat wildlife and anything else they can get their paws on.''