Cat owners on Bruny Island who continue to let their felines stray could be slapped with a $600 fine under tough new laws to crack down on wildlife killings and feral populations.

Key points: Kingborough Council passes new by-laws to help reduce the killing of wildlife

Kingborough Council passes new by-laws to help reduce the killing of wildlife Cat owners will have to register cats and have them de-sexed before six months of age

Cat owners will have to register cats and have them de-sexed before six months of age Owners face $600 fines if they fail to comply

Every year in the Kingborough Council region in southern Tasmania, 180,000 native animals are killed by domestic cats alone.

The new laws will be exclusive to Bruny Island, which contains an estimated 2,000 feral cats, and be the toughest in Tasmania.

They include compulsory registration, de-sexing of domestic cats before six months of age, and a limit of two cats per household in the absence of a permit.

Council's cat management officer, Kaylene Allan, said while most owners on the island were doing the right thing, action was needed.

"It's the first comprehensive by-law in Tasmania and we're hoping it might be a model for other councils," she told Leon Compton on ABC Radio Hobart.

Bruny Island is home to many species of endangered birds and animals. ( ABC News )

Cracking down on wandering cats

Globally, cats are listed as one of four species that threaten the greatest number of endangered native animals.

Feral cats kill 466 million reptiles and 272 million birds in Australia annually.

Most cat owners surveyed on Bruny Island already de-sex and microchip their cats, but almost 60 per cent were letting them roam.

"They need to keep their cats on their property," Ms Allan said.

She said it would be up to owners to decide how they restrict their cats; whether it was by keeping them inside, using better fences or constructing outside enclosures.

"All cats that either reside permanently on the island or regularly visit the island will need to be registered with council.

"They have to be kept within their owner's property boundaries at all times, unless they are on a lead or restrained in a car.

"If there is a complaint against your cat and your cat roams regularly on your property boundary then we will be taking action," she said.

This cat was spotted with a shearwater in its mouth at The Neck Game Reserve. ( Supplied: Kingborough Council )

Ms Allan said the impact of domestic and stray cats on native mammals and birds was greater where cats lived adjacent to bushland areas and reserves.

Under the laws, the feeding of stray cats will also be prohibited.

"We're trying to make it as consistent as possible with the control and management of dogs so it's fair and reasonable," she said.

"We believe we've got the balance right."

Laws are 'strict'

Mayor Dean Winter said he didn't personally agree with the by-law.

"It is quite strict — cat owners have been tasked with an onerous set of responsibilities," he said.

"I think we'll see how that plays out in terms of whether council is able to educate the community about these new by-laws."

The laws on Bruny Island will come into effect later this year.