A rat is believed to have made it on to the Tiritiri Matangi island reserve, and a large-scale response is underway to find and eradicate it.
The Department of Conservation today said footprints were found inside a tracking tunnel on the island, showing a rat had passed through some time between New Year and January 7.
Since then, two pest-detection dogs and handlers were sent to the island, and 50 additional traps and 60 additional tracking tunnels have been deployed.
Tiritiri Matangi is home to takahe, kiwi, kokako and little spotted kiwi and has been pest free since 1993.
There are also tuatara, wetapunga and five types of native lizard on the island.
It is more than 3km from the mainland and DOC said it is no known how the rat made it, but visiting vessels were most likely to blame.
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