Tiritiri Matangi was put on high alert in early January after rat tracks were detected on the island sanctuary, home to kiwi, takahe and tuatara among other protected wildlife.
Two pest detection dogs were deployed to sniff out the rodent and the Department of Conservation deployed an additional 50 traps and 60 extra tracking tunnels. The rat was finally trapped and instantly killed in a DOC 200 trap on Friday 26 January.
Later in the month members of the public have reported seeing a black cat on the Islington Bay near the causeway between Rangitoto and Motutapu islands, which have been free of cats, rats, possums and mice since 2011.
Motion-sensitive cameras, cat-tracking devices and traps were deployed, along with conservation dogs, trained to detect cats, but the operation was scaled back after 10 days when no activity was detected.
DOC is calling for boaties to be especially vigilant about biosecurity measures when visiting the Hauraki Gulf islands and to leave their pets at home.