A single cat may be a threat to one of Wellington's best known wild-life reserves.

The Department of Conversation is investigating a potential sighting of a feline on Mana Island.

Since the cat sighting, DOC has increased its surveillance regime, and deployed 14 motion detection cameras.

Wellington Biodiversity Ranger, Colin Giddy says they've also sent out a dog handler with three cat-detecting dogs to search for any sign.

Mr Giddy says the presence of a single pest could create devastating effects for the natural wildlife - particularly given the amount of threatened and endangered species on the island.

Mana Island has been pest-free since 1990.