The Society for the Prevention of Cruelty to Animals (SPCA), concerned by the growing number of stray cats on St John's Island, is returning there on Jan 18 to neuter them and contain their numbers.

The team of 24 SPCA staff, vets and volunteers will spend three days on the island. They will trap the cats, neuter them in planned surgeries, then release them.

The SPCA had noticed "an alarming number" of unsterilised cats on the island during their previous neutering exercise last November when it neutered more than 30 cats, said SPCA executive director Corinne Fong.

Some were purebred cats, which the SPCA has said may have been abandoned by their owners.

"We aim to sterilise as many as is humanly possible," she said.

Animal welfare groups have been consistently calling for a national effort to sterilise stray dogs and cats, to help control their numbers and reduce the need for the authorities to cull them.