Biosecurity

Pest animals

New Zealand was isolated for thousands of years, allowing many of our native animals and insects to evolve without fear of predators or people. We also have no native land mammals except for bats.

When people started arriving here, they brought with them (not always intentionally) many different animals that had no natural controls here. 

Some of these animals have become our worst predators – mainly rats, mice and stoats. Others, such as possums and rabbits, are devastating our native forests and grasslands. 

Animals brought here for farming or domestic needs have also over time escaped and bred in the wild, for example pigs, goats and deer. 

There are also some more recent arrivals that have become pests, like wasps, Argentine ants and rainbow skinks (also known as plague skinks).

Our native plants and animals have not had time to develop defences against these predators, and  they need our help  to survive.


Environmental impacts

Pest animals have a significant impact on our native plants and animals.

  • They harm native birds, invertebrates and mammals like the bat, either attacking them directly or competing with them for food or habitat. 
  • They destroy habitat for these species through their destructive behaviour in native and plantation forest, particularly feral goats, deer and possums. 
  • They harm agriculture, by damaging fences and pasture, and species like possums and pigs can spread diseases like bovine tuberculosis.
  • Feral pigs are also a likely vector for soil-borne diseases like kauri dieback disease.

The freshwater environment is also at risk from introduced fish species, like koi carp, brown bullhead catfish and gambusia. These fish can impact on recreational values, water quality and/or aquatic biodiversity.


Key pest animals

Each pest animal identified in the Regional Pest Management Strategy has its own specific management approach.

Our strategy is to target pest animals that are:

  • in low enough numbers to be containable
  • a threat to important habitats or native species.

For more on each species, click the heading below.

Argentine ants are among the 100 most invasive species in the world. They threaten native birds, insects and lizards by attacking them directly or competing with them for food. They can also become a major household and garden pest.
Argentine Ants (PDF 1.3MB)

An argentine ant
Image credit: Richard Toft 
Possums can destroy native forest canopy and prey on native birds and birds’ eggs and invertebrates.  They also compete with native species for food.
A possum 
Rats and mice prey on native bird eggs, bird chicks, invertebrates, and lizards.  They also eat native seeds and mice compete with native species for food, eating almost anything.
Rats 
Image credit: David Mudge, Nga Manu Images
Mustelids can attack native species, including birds like kiwi, insects like weta, lizards and frogs. Ferrets can also spread bovine tuberculosis.
A stoat
Image credit: Landcare Research 
Rabbits can cause considerable physical and economic damage. They eat commercial crops, compete with stock for pasture and eat forestry and plantation seedlings in winter and spring.
A rabbit 
Feral pigs root up the ground and eat native plants and insects, invertebrates and ground nesting birds and their eggs.  They can also spread diseases like kauri dieback.
A feral pig 
Feral goats are opportunistic browsers and are destructive in native forest, eating the foliage of most trees and plants, including seedlings and saplings.
A feral goat 

Feral deer destroy the understorey of native forest by over-browsing, grazing, bark stripping and trampling, which in turn may increase soil erosion.

Report any feral deer to biosecurity at biosecurity@aucklandcouncil.govt.nz or 09 301 0101.

Learn more about feral deer control.
A feral deer 
Plague skinks (also known as Rainbow skinks) breed and mature quickly. They can reach high population density in a short time and outcompete our native lizards and other species for food and habitat.
Plague skink (PDF 582KB)
A rainbow skink 
Wasps are major predators of invertebrates and compete for sugar resources with nectar feeding birds and insects. They can also inflict painful, toxic stings on humans and animals.
A wasp 


How to stop pests from spreading

To avoid spreading pests unintentionally, always check your gear thoroughly for pests and clean your gear between different sites.

Be extra careful to check for small pests like Argentine ants, rodents and rainbow skinks.

This is particularly important if you are travelling to an offshore island, which are often free of all, or some pests. 

For more detailed information on this, see Visiting the Hauraki Gulf Islands

Cleaning gear between sites will also minimise the spread of weeds and soil-borne diseases like kauri dieback disease.

A red-eared slider turtle
Red-eared slider turtle.

Please also avoid releasing any pest animals into the wild. This includes unwanted pets like mice, red-eared slider turtles, goldfish or rainbow lorikeets.

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