NPWS scientific officer Les Mitchell said the service was concerned about the damage cats caused in reserves and parks.

“The impacts can be devastating because cats are natural-born killers,” Mr Mitchell said.

Cats target small birds such as blue wrens, reptiles such as skinks and small mammals including native mice.

Mr Mitchell said the NPWS was not calling for a ban on cats.

“We are aware that cats do make a good companion animal for people,” he said.

The service wants more cat owners to consider local native animals.

Mr Mitchell said that because cats were nocturnal hunters the service would like cat owners to keep their pets inside at night.

The problem arose when reserves and national parks were close to urban areas.

Mr Mitchell said there were no laws governing cats and the NPWS only had the power to act if cats went into restricted areas like parks and reserves where native animals lived.

He said the service did not commonly trap cats but carried out public education programs encouraging cat owners to be more responsible.

Mr Mitchell said cats were not the most lethal threat to native animals.

“Cats are number two and foxes are number one. Foxes are a problem because they kill larger animals,” Mr Mitchell said.

RSPCA West Nowra Animal Shelter manager Amanda Elleman said she advised people to keep their cats inside or build them a run so they didn’t get into reserves.

Ms Elleman said that for the cat’s own safety it was better to contain them.

She said cats were randomly trapped, some gassed and others taken to the shelter.

Ms Elleman added if a cat was enclosed it would be less vulnerable to diseases such as feline AIDS or to accidents.

In fact, pet cats that are prevented from roaming have been found to live longer than those that are allowed to range freely.