Te Punga o Te Waka a Maui, is the original Maori name for Rakiura Stewart Island. It translates as "The Anchor Stone of Maui's Canoe" placing New Zealand's third largest island at the heart of Maori mythology surrounding the discovery of Aotearoa.
Using a magical fish hook, Maui, the mythical Polynesian voyager, is said to have hauled New Zealand's North Island, Te Ika a Maui (the fish of Maui) from the ocean depths from his canoe, the South Island, Te Waka a Maui (the canoe of Maui) while it was anchored by Rakiura Stewart Island.
Today, the name Rakiura records the island's Glowing Skies, a reference to the Aurora Australis, or Southern Lights. The European name for New Zealand's most southerly inhabited island where around 400 people live permanently and 30,000 people visit annually remembers William Stewart, the mate on the sealing ship Pegasus, who charted Port Pegasus in the south of the island in 1809.
Three Rats, Feral cats
Given the size of Rakiura Stewart Island, expert advice is that eradicating mammalian predators using toxins is the only feasible methodology amongst current technologies.
However, rather than attack the whole island at once, building a predator proof fence around the main settlement of Half Moon Bay would allow the eradication methodology to be tested and proven on a large area, with minimal risk of re-invasion from beyond the fence, before being scaled up to the rest of the island, if successful.
Once the island wide eradication project was completed, the fence would then become a firebreak to guard the island against any predator re-invasion event that did occur as a result of visitors and freight arriving in Half Moon Bay either by sea or air.
Eradicating predators from Rakiura Stewart Island would provide significant ecological, social and economic benefits.
Ecological benefits include removing predation from endangered wildlife such as southern New Zealand dotterel, endemic bats, Fiordland crested penguins and Stewart Island robin. Vulnerable, gradually declining species including Stewart Island kiwi, yellow-eyed penguin and yellow-crowned parakeets would also recover.
Social and economic benefits would come from jobs directly created by the project and from increased tourism demand that would likely result from more visitors to Rakiura Stewart Island.
The jewel in the crown will be returning kakapo to the island.
A Predator Guild
Predator Free Rakiura is an extremely ambitious concept. Rakiura is a very large island and the target predators are a very large group of species.
Attempting the eradication of six different predators on a very large island is probably unique. This diversity of animals overlaid onto the diversity of the island's habitats makes for a bewildering array of ecological relationships that need to be considered.
Community ecologists use the concept of a guild to describe a group of species that need not be closely related but which all exploit similar resources. All the target species prey on native fauna so together they form a predation guild.
However, they also have interspecific relationships that make things more complex. Feral cats prey on rats and black and brown rats prey on kiore. There will also be competitive pressures between these species, particularly when resources are scarce.
Because of their relationships, dismantling this predator guild will be difficult and may generate perverse outcomes. Removing rats may cause cats to prey switch, putting more pressure on native wildlife. Removing cats may cause rat numbers to increase even further.
In any case it will be costly. In every case the benefits will be huge.
Ulva - An Island's Island
Within the sheltered waters of Paterson Inlet, Ulva Island shows what Rakiura Stewart Island could become if mammalian predators were eradicated.
This forested 266 hectare island has been a reserve for nature since 1899, making it one of the first such reserves in New Zealand. It has never been logged or had browsing animals so it is as close to pristine southern forest as can be found.
Rodents have been eradicated from the island but being, in places, less than one kilometre offshore from the main island means rats do periodically arrive. These are controlled by a network of permanently installed trapping stations.
Resident birds such as Stewart Island weka, South Island kaka and both red-crowned and yellow-crowned parakeets now share the forest with translocated South Island saddleback, Stewart Island robin, rifleman and yellowhead. There are also 30-40 Stewart Island brown kiwi (Tokoeka) present. See a slideshow of these birds here.
Today Ulva Island is a predator free open sanctuary that is a short water taxi, or regular ferry ride from Golden Bay near Oban. With 4.5 kilometres of high standard walking paths it is both a trip back in time to how Rakiura Stewart Island once was and a trip forward in time to what it may again become if predators can be eradicated.