This week I am visiting 3,455 ha Norfolk Island, north of New Zealand. Although closer to New Zealand, Norfolk Island is an external territory of Australia, currently governed by its own general assembly. Norfolk Island is the last island around New Zealand from which we need a genetic sample of the invasive rats to complete our phylogeographic map of invasive rats around New Zealand and neighbouring islands. The Pacific rat first arrived on Norfolk Island with Polynesian colonists nearly a thousand years ago. Although the Polynesians did not stay on Norfolk Island, the rat that came with them, subsequently known as the Polynesian rat, did. Only more recently has the black, or ship, rat arrived with Europeans, this time around World War II, when it was spread to so many islands in the Pacific, often in association with runway developments, such as occurred on Norfolk Island. There has never been a record of the brown rat arriving. Once we have all the rat samples we will be able to chart the arrival and spread of invasive black and brown rats in New Zealand. So on Norfolk Island I will be setting lines of traps in suitable rat habitat and checking them every day to get my precious sample.
Offshore from Norfolk Island are two smaller precious islands saved from the ravages of invasive rats and other predators such as cats. Phillip Island towers on the horizon to the south from our accommodation at Heritage Hill, which doubles as our field laboratory. Although cats and rats were never introduced to the island, goats, pigs and rabbits all were, and the habitat and plant destruction which took place prior to their eradication in the late 1980s is still visible as scars on the landscape. However, now the island is a haven for nesting seabirds of all types. Closer to shore is the smaller Nepean Island, currently covered in nesting seabirds. At only 2 kilometres offshore it would be vulnerable to swimming brown rats, but thankfully that species was never able to colonise Norfolk Island, possibly because of competition from incumbent rats on the island which had arrived first. It is important to remember that not all invasive rat species are the same.
Tonight I am giving a talk to local Flora & Fauna Society, and I will update later in the week with the success of my rat trapping and some more of the colourful history of Norfolk Island.