Frequently Asked Questions
Why is the Tū Mai Taonga project needed?
Unfortunately, current efforts to manage feral cats and rats on Aotea is not enough to protect our most vulnerable species.
In 1994 the last two kōkako on Aotea were removed to Hautūru, Little Barrier Island to prevent them being eaten by rats.
Other species lost to the island since European settlement include the tūturuatu (shore plover), hihi (stitchbird), tīeke (saddleback), koitareke (marsh crake), popokatea (whitehead), pipipi (brown creeper), tītipounamu (rifleman), yellow-crowned kākāriki, tītī (sooty shearwater), kuaka (common diving petrel),tuatara, pekapeka (short-tailed bat) and pūpūharakeke (giant land snails).
Although Aotea is free of possums, mustelids and Norway rats, some species are only just hanging on despite widespread efforts to trap ship rats, kiore and feral cats - like the oi (grey-faced petrels) which are still scattered around cliffs, the reintroduced toutouwai (North Island robins), and rare miromiro (tomtit), the vagrant korimako (bellbird), red-crowned kākāriki, matuku (bittern, mātātā (fernbird), mioweka (banded rail), pāteke (brown teal), tītī (Cook’s petrel), tūturiwhatu (New Zealand dotterel) tākoketai (black petrel), pepeketua (Hochstetter’s frog), Duvaucel’s gecko, moko kākāriki (Auckland green gecko) and the niho taniwha (chevron skink).
The good news is that the benefits of sustained predator control is being seen in island sanctuaries at Windy Hill (where more than 60,000 rats and nearly 400 feral cats have been removed over 23 years), Glenfern and Motu Kaikoura.
Bird counts at Windy Hill show increasing abundance of kererū, tūī and kākā, a trend that has been reflected across the island since 2006.
Tū Mai Taonga is an opportunity to build on these success stories, initially the Aotea Conservation Park and north of Aotea. Once techniques and methodologies are proven and the community is ready, the project will look to extend operations across the whole of Aotea.
Why are feral cats a problem?
Feral cats are expert hunters and have a diverse diet often heavily focussed on native species. This is because our native species evolved in the absence of predators like feral cats and so have few natural defences. Feral cats eat adult birds, chicks, eggs, geckos and skinks. In Aotearoa, feral cats have contributed to the extinction of 9 native bird species and impact on 33 now endangered species.
They are quite different animals from the average domestic cat, which maintains a small core area of home range, often as exclusive property. Feral cats on the other hand, have much larger home ranges which may overlap with those of other cats. Range size can be anywhere from 48 to 700 hectares, but even up to 2000ha on Rakiura/Stewart Island. It all depends on habitat, food availability and, for males, where females are.
Feral cats, particularly kittens, have a shorter life span than domestic cats. House cats commonly live for 15+ years whereas feral cats may only live for about 6 years. It's a hard life in the wild, despite the presence of easy food. Most kittens are born between spring and summer which is often when we see them on Aotea.
Because they range widely and need a lot of energy to survive in the wild, feral cats can do significant damage. Like most predators, they are tuned into 'easy wins' in their environment such as where colonies or gatherings of their prey species are. On Aotea this includes tākoketai, black petrels on Hirakimatā, pāteke at Okiwi and elsewhere, oi (grey-faced petrels) on the coast, and tūturiwhatu, dotterel at Whangapoua. Kākā and kākāriki chicks fledge out of nests and onto the ground and are also very vulnerable to cats when young.
While feral cats are known to eat rats, rat breeding rates and densities are so high in the Aotea bush that feral cats are unlikely to have any more than a limited effect on overall rat numbers.
Why are rats a problem?
Rats are far more numerous than feral cats because they are so well adapted to our conditions. Rats have a short lifespan (about 17 months) and are fast breeders (every 6 to 8 weeks in summer and autumn). They can breed more quickly when there is more food, and in ideal conditions rats can produce up to 10 offspring at a time. In temperate northern environments like Aotea, rats may breed all year round, where there is abundant food and shelter.
There are two rat species on Aotea: kiore, the Pacific or Polynesian rat (Rattus exulans) which arrived with Polynesian voyagers, and the more damaging ship rat, or black rat (Rattus rattus) which arrived in the mid-1800s. These invasive rats pose a greater threat to island wildlife than any other at the present time.
Ship rats are found from the coast to the treeline and spend a lot of time in trees, so as well as damaging your orchard and crops, wiring and buildings they can strip forest trees of berries and nests of chicks and eggs.
Kiore numbers are often influenced by where ship rats are not. Ship rats are their competitors and can keep kiore numbers down. Therefore it's important to control both species at the same time.
Rats are damaging because they reduce bird numbers directly by eating both chicks and eggs, herpetofauna (frogs, geckos and lizards) and invertebrates.
Rats also compete with birds for food and damage the forest by eating seeds and seedlings. This means there are fewer birds spreading seeds to regenerate the forest. The cumulative effect of rats doing this damage is that the forest is less able to recover and is less resilient to fire and other stressors.
What can we do about these predators?
The Tū Mai Taonga project has commissioned an independent technical feasibility study to consider the best ways to protect and restore native species and ecosystems through feral cat removal and intensified rat management, initially in the Aotea Conservation Park and Northern Aotea area.
The report will be completed early in 2022 and reviewed by a Technical Advisory Group and the Project Steering Committee before discussion with the community and landowners. Keep an eye out for updates.