The discovery that a boatie's cat had roamed a pest-free wildlife haven for almost five months without detection has sparked a biosecurity shake-up in the Bay of Islands.

The cat had been taken sailing by its Northland owner in December but jumped overboard near Urupukapuka Island and swam to shore. The owner did not report the cat's escape and it was only discovered in May when it wandered into Otehei Bay, near starvation and with a paw hooked through its collar. The cat was taken to a vet who returned it to its owner.

The find was a shock to the Department of Conservation and volunteers behind Project Island Song, a community-led project to eradicate pests and restore native wildlife in the eastern Bay of Islands. The toutouwai (North Island robin) was re-introduced to Urupukapuka in 2014 and the endangered tieke (saddleback) in April this year.

Guardians of the Bay of Islands chairperson Fleur Corbett said the fact a cat was able to go undetected for so long was a wake-up call.


"We thought we had good biosecurity. This prompted us to review all our biosecurity measures. It's a worry - we have rare birds on the island, and by that stage we had tieke there too."

DoC ranger Adrian Walker said Urupukapuka was searched afterwards by a dog trained to sniff out cats but no further felines were found. The islands' biosecurity plan now included an annual sweep for cats. From the cat's scat it appeared it had been eating invertebrates such as weta and cockroaches. It may have also eaten lizards, native birds and young blackbirds and thrushes. There are no mice or rats on the island.

The owner was not prosecuted or formally warned because the cat was not intentionally released on the island.

Mr Walker urged boaties not to take their cats anywhere near pest-free islands, and ideally leave them at home altogether. In 2009 a pair of Auckland boaties took their dog ashore at the strictly protected Poor Knights Islands, off Tutukaka, to go to the toilet. They were reported by another boatie and charged in the Whangarei District Court with entering and allowing a dog to enter a controlled nature reserve.

They were granted diversion after paying $1000 towards conservation work on the islands, which are tapu to Ngatiwai and home to rare wildlife such as the tuatara and giant weta.

In 2002 Auckland boaties Mark and Carolyn Craft were fined $2600 after they took their pet ferrets for a walk on Great Barrier Island.

The outcry that followed led to a law change banning the keeping of ferrets as pets.

- Project Island Song feature - page B1