SPCA further supports legislation that enables local councils to pass bylaws to manage cats to protect biodiversity, including the registration of cats on a government database.

The National Cat Management Strategy Group (members include SPCA, the New Zealand Veterinary Association, the Morgan Foundation, Local Government New Zealand, Companion Animals New Zealand, and observer members MPI and DOC) has extensively reviewed cat management in New Zealand. They recommend comprehensive cat management legislation that requires companion cats to be desexed, microchipped and their microchip registered, and kept at home.

The current ad hoc approach to cat management does not fully address harms to cat welfare harms to other animals and people as a result of cat overpopulation.

Cat welfare problems related to cat overpopulation include:

• the predictable cycle of unplanned litters of kittens born each year because there are too many cats that are not desexed and they are allowed to breed;
• cats and kittens who are lost or have strayed, but cannot be reunited with their owner because they are not microchipped, or their microchip details are not registered on a national database; and
• the majority of cats and kittens who enter animal shelters and rescue organisations are in need of care because they have contagious diseases, are injured, or lost because they roam freely from home.

Problems with cat overpopulation include predation on wildlife, and the spread of toxoplasmosis to people, farmed animals, and vulnerable native marine mammals (e.g., Hector’s and Māui dolphins). Problems with cat overpopulation also can lead to nuisance in communities (e.g., spraying, toileting, fighting).