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Mammals and native wildlife

Mammals and native wildlife

Updated 24 April 2014 3:51pm

Club rush


New Zealand has a diverse and unique set of native species, but unfortunately we also have a large number of introduced animals and plants that put pressure on them. Because there were originally no mammals here (apart from bats, dolphins and seals), our native animals have not evolved to compete against mammals, so they are particularly vulnerable to mammalian predators.

This page contains information about cats, rats and mice, possums, stoats and hedgehogs.



Common skinkDomestic and feral cats are a big threat to native wildlife. The SPCA and Forest and Bird estimate that 47% of all households have a cat. The high density of domestic cats in towns and cities puts hunting pressure on our wildlife.

Many native forest birds are particularly vulnerable when they first leave the nest. They may spend several days on the ground before they leave home for good, and most are naive about predators - they've evolved without cats being part of the environment. And cats don’t just eat birds, they also eat bird food: insects, butterflies, moths and lizards, reducing a valuable food source for kōtare (kingfisher) and others.

Cats hunt at any time of the day or night, when native birds are roosting, or during the breeding season when they and their young are on their nests. Cats are often active hunters at dawn and dusk, so a good way to protect wildlife is to bring your cat inside in the evening, and keep it inside until morning.

What do we know about the effect of cats on wildlife?

The best information about the effect of domestic cats on wildlife comes from a Department of Conservation / Forest and Bird Society study done in Wellington in 2000. In that study 130 pet cats were monitored over 3 months. In that time they brought home 267 birds, 183 skinks (mokomoko), eight geckos, 64 insects, 67 rats, 314 mice, one stoat and three rabbits.

While cats do play a role in keeping rat and mice numbers down, there are better ways to control these animals that don't also harm native wildlife. You could lay poison bait or set rodent traps on your property.

What can I do to stop my cat hunting?

The only way to completely stop a cat from hunting would be to keep it inside at all times. This isn't practical for most people, so we recommend the following:

  • Keep your cat indoors at night - from dusk to dawn. A good way to do this is to bring the cat inside in the evening and not let it out again until morning.
  • Get your cat de-sexed. Unwanted kittens learn to prey on wildlife.
  • Never dump a cat. Dumped cats will prey on wildlife or can starve.

For more information on how to protect native wildlife, the SPCA and Forest and Bird have published a Code of Responsible Cat Ownership. You can also check out information about feral and unwanted cats.


 Rats and mice

Rats and mice are major predators of native wildlife and also consume the food that natives eat. Rats not only eat fruit and seeds that feed native birds, they also eat eggs, chicks and nesting adult birds. Mice even eat whitebait eggs on riverbanks.

Rats usually only come out at night so many people do not realise how many there are. They are prolific breeders with up to five litters per female each year and up to 14 babies per litter.

Rats eating eggs - Nga Manu images
How can you help reduce rodent numbers?

Keeping rat and mouse numbers low is one of the best ways to encourage the return of native birds and wildlife. Rat and mouse traps and various baits are available from shops, garden centres and home supply stores. Having a rat or mouse trap in your garden, especially if you live near native bush, is a great way to help our native plants and wildlife.

When rats and mice eat fruit and seeds they prevent our native plants from reproducing. In years when the forests produce a lot of these rat and mice populations often explode because of the abundant food source. The high rat and mice numbers then puts pressure on native wildlife.

There is more information about rats and mice here.



Possums are revered in Australia. Don’t let that stop you trapping and baiting as many of ours as you can!

There are millions of possums in New Zealand, and each night they chomp their way through thousands of tonnes of forest. It's not well known that possums also eat birds’ eggs, young chicks and insects. When possum numbers are reduced, by using traps or poison, bird numbers soon recover and the health of our forests improves.

If you live near native bush it's easy to install and operate a possum trap. The National Possum Control Agency has more information about traps and baits. You can also find information here.



Stoats and other mustelids (ferrets and weasels) are lethal to our native wildlife. They are one of the main reasons why birds like weka and kiwi are almost gone from New Zealand's forests.

Stoats are excellent climbers and very good at finding nesting birds. They are also very aggressive and have sharp teeth and claws. Adding to the problem is their ability to quickly reproduce, and travel large distances in search of food. Overall, stoats are one of the worst predators of New Zealand's native wildlife.

Stoats, ferrets and weasels are present throughout the Wellington region, including in our cities. Unfortunately, mustelids are very difficult to trap. Some new traps are now available, but you may need experience or training to make the best use of them.

The Department of Conservation has more information about these traps. A good way to learn more about trapping mustelids and other pests is to contact one of the volunteer groups working in the region. These local heroes are helping to make our forests safe for native wildlife.

You can find out more about mustelids here.



Many people don’t realise that hedgehogs also put significant pressure on many of our native animals. They can range over surprising distances in one night, eating insects and lizards along with the eggs and chicks of ground nesting birds.

You can use mustelid traps to catch hedgehogs and help to protect our native animals. For more information, check out the Department of Conservation.