Pests

Tiritiri Matangi was a prime location for a restoration project because it was relatively pest free - cats, possums, Norway and Ship rats as well as mustelids were never transported to the island. Indeed, since the 1800s only a couple of pests have established themselves on the island.

Kiore

At the time the restoration project was launched in 1984, there was only one pest on the island; the kiore. Once thought to be vegetarian, it was discovered that in fact these small Polynesian rats ate berries, eggs, chicks, frogs, insects and lizards. Records show that at certain times there was a population explosion with records of 200 kiore per hectare which no doubt had a devastating impact on the ecology. 

After preparing a plan to help safeguard the Island’s wildlife, a helicopter drop of anticoagulant brodifacoum was carried out in 1993 in an effort to eradicate kiore. Ninety percent of pukeko were killed after the poison drop and brown quail, blackbirds, sparrows and mynas were also decimated. However threatened species such as kiwi pukupuku (little spotted kiwi), tieke (North Island saddleback) and toutouwai (North Island robin) populations were not detrimentally impacted. Following the drop, kākāriki and koera (brown quail) enjoyed a population boom and plant species such as kohekohe and native broom flourished. The effectiveness of the kiore eradication on Tiritiri Matangi has led to eradication projects on larger islands, such as Kapiti in 1996 and Little Barrier Island in 2004.

The ongoing  success of Tiritiri Matangi is dependent on the island remaining predator free and so continual vigilance and education is required to ensure it keeps its pest-free status.

References:

Anne Rimmer (2004) Tiritiri Matangi; Tandem Press, Auckland New Zealand

http://www.gbict.co.nz/Newsletters/Issue7/Island Rat Eradications

Argentine Ant

The vigilance of a Department of Conservation entomologist led to the discovery of Argentine ants near the wharf in 2001. It is thought that this incredibly invasive species arrived on an infested dinghy. 

An initial survey showed they were already well established having created a number of nests near the wharf and North East Bay, so an eradication programme was launched. Another infestation occurred in 2008 around Hobb’s beach which lay close to the wharf. 

Argentine ants eat a wide variety of foods, attack nesting birds and kill nestlings, and disrupt native ecosystems displacing native ant species. They produce multiple queens and can form super-colonies that extend for thousands of kilometres.

The eradication of this emergent super colony involved hand laying bait at 2-3m intervals on a grid with the help of volunteers. 

In 2016, eradication was achieved. This is the first time a total eradication of ants has been achieved in such a large area of New Zealand.

To prevent another outbreak of Argentine ants, we encourage visitors to check their gear for stowaways like the Argentine ant as these pests can have a devastating impact on the island’s wildlife.