On-the-ground signs of an unhinged cat boom in Southland continue to emerge, with a local animal charity saying it spent $18,000 in feline vet bills last month.

Furever Homes says it receives 100 calls a day about animal issues, most of them relating to cats and kittens. Up to six of those messages are an urgent request for the cats to be taken on the spot. 

Founder Donna Keil said cases the charity had be involved with included at an Invercargill property where 10 cats had been left behind, three of which were pregnant, and a further six were found dead in a wheelie bin. 

Last month, Mrs Keil said they had rushed a kitten to the vet that was found in a declining state under a cafe in Mossburn. 

For that reason, she said the volunteer-run charity was starting to reach its breaking point. Mrs Keil said they used to focus more on dogs, but over the last year it's been an "absolute increase" in cats, to the point where it felt like there was no longer a breeding season. 

Last month it spent $18,000 on cat desexing, vaccinations, worming, and treating infections alone. 

"It is fully out of control, not only in Southland but we also work with Alexandra who have no support except from a small group of local volunteers. Queenstown Cat Rescue are also under the pump."

Even in more isolated regions, something seems to be changing. Te Anau resident Sonya Harris said she put in two more cat traps on her farm last week, for a total of nine, to safeguard the rare chickens she breeds and shows. 

She said she was catching a lot more feral kittens than in previous years, a sign there were more older cats breeding in the area.

"I could catch maybe three or four a week in the breeding season and they could be different ages, which means that they're from multiple parents."

She said she tried to domesticate and re-home the cats she caught, but the growth was a concern both for her chickens and the native wildlife at a nearby wetland. 

"As each year goes past, I'm only catching a fraction of what's being produced out there."

Te Anau resident Lynette Todd began trapping feral cats this year, after seeing how easy it was to tame them while they were still kittens. A trap she recently placed at Te Anau's boat harbour caught four feral kittens. 

She's started to coordinate interested volunteers to help re-home cats, moderates a Fiordland cat rescue page on Facebook, and she's hoping to set up a fund to cover desexing procedures in town. 

"What we don't want to happen is them to be spreading out all over the place killing all the birdlife."

As for reasons behind the perceived boom, Mrs Keil pointed to a decline in desexing. It seemed fewer people were desexing the free kittens they got online, perhaps due to the unexpected costs of owning a pet.

Fewer rentals were allowing for cats, meaning a move could leave the pet cat behind. Cats could also simply outlive their elderly owners, putting them back out in the open. 

Furever Homes went to Parliament this month, along with other animal shelter charities across New Zealand, to advocate for their case to Green Party MP Gareth Hughes. 

"Animal welfare in New Zealand is reaching third-world country levels, it's absolutely shocking," she said. 

Advocate South was unable to reach the either the National SPCA or its Invercargill branch for comment before press time.

Last year we reported that for authorities, getting a sense of feral cats, especially in sensitive areas, was a difficult task.

Environment Southland biosecurity and biodiversity operations manager Ali Meade said the regional council didn't have a good record of cat numbers across Southland as feral cats were secretive and often nocturnal.

"But new technologies such as trail cameras are giving us an insight into feral cat distribution and cats have been seen in bush blocks, river beds, farmland and wetlands."

Environment Southland's controversial Southland Regional Pest Plan proposal, released last year for public submissions, is still with the hearing panel.

The proposal received international attention for introducing new rules requiring domestic cats to be neutered and microchipped in Omaui, near Invercargill, with cat owners having six months from the rules taking effect to register their cats with the regional council. After six months, new domestic cats wouldn't be allowed in Omaui.

Existing rules on Stewart Island would also continue so that all domestic cats were neutered and microchipped. 

Environment Southland staff said they could not make any comment on those proposal yet, but were hoping to have a decision by the middle of June.