Predator control in your backyard

Plant all the kōwhai and flax you like. If ship rats run along your fence line every night, the tūī and pīwakawaka (fantail) nesting in your hedge will struggle to raise chicks. Introduced predators are one of the biggest threats to New Zealand's native birds, and backyards are part of the picture. The upside is that a few well-placed traps, checked regularly, really do help, especially when the neighbours join in.

This field note covers which animals to target, the traps that suit a suburban section, how to keep children, pets and birds safe, and when a problem is bigger than a backyard trap.

Know your target

Ship rat (Rattus rattus). Slim, agile, with a tail longer than its body. Ship rats are superb climbers and reach nests high in trees, taking eggs, chicks and sometimes sitting adults. In towns they travel along fences, power lines and branches, and they often live in roof spaces.

Norway rat (Rattus norvegicus). Bigger and heavier, with a shorter, thicker tail. It is more of a ground-dweller and is usually found around buildings, drains, compost and streams.

House mouse. Small, but they eat insects, seeds and lizards. Numbers can boom after a heavy seed year.

Stoat. DOC calls stoats the number-one killer of many of our endangered native species. They were introduced as early as 1879 to control rabbits. Stoats take eggs, chicks and sitting adults, can swim more than a kilometre to reach islands, and young stoats have travelled over 70 km in two weeks. They are less common in the middle of cities but turn up on the edges of towns and near bush and farmland.

Possum. Possums browse native trees, but they also eat native birds and their eggs, and they compete with kererū (New Zealand pigeon) and tūī for fruit and flowers.

Hedgehog. Many people are fond of them, but hedgehogs eat the eggs and chicks of ground-nesting birds as well as lizards, wētā and native snails. DOC's hedgehog page sets out the damage they do on braided rivers and how to trap them.

Cats are also major bird predators. For a pet cat, the simplest steps are to keep it inside at night, put a bell on its collar and have it desexed.

Choosing traps for a suburban section

For most backyards, trapping is the safest choice. It avoids putting poison into the food chain or within reach of pets. DOC recommends using traps that have passed the National Animal Welfare Advisory Committee (NAWAC) testing guidelines, and putting at least one trap or bait within each target animal's home range. See DOC's trapping guidance for communities before you buy.

• Snap traps in a tunnel. A good-quality rat snap trap set inside a wooden or plastic tunnel is the backyard staple. The tunnel steers the rat onto the trigger and keeps birds, pets and small hands out.
• DOC 200 (and DOC 150/250). These run-through box traps are mainly aimed at stoats, and they also kill rats, hedgehogs and larger weasels. They suit larger sections, the edges of reserves, and community trap lines.
• Self-resetting traps. Gas-powered resetting traps cost more but keep working between checks. They're useful if you can't check traps often.
• Possum traps. Kill traps for possums are usually fixed to a tree trunk at a height that keeps them clear of pets. Check local rules and the trap's own instructions.

Baits. Peanut butter works well for rats and mice. For stoats and hedgehogs, think meaty, fishy or eggy. Rotate baits now and then, as animals get bored of the same lure.

Placement. Put traps where animals travel: along fence lines, beside buildings, under hedges and near compost bins. Rats rarely cross open lawn if they can avoid it.

Safety for children, pets and birds

• Always use a tunnel or box. An open snap trap on a lawn is a hazard to blackbirds, fantails and fingers.
• Choose the right entrance size. Small entrances keep cats and dogs out. Follow the maker's guidance and don't modify trap boxes.
• Check traps at least weekly, and more often at first. Remove dead animals with gloves and wash your hands afterwards.
• Be very careful with poison. If you do use rodenticide, keep it in a locked, tamper-resistant bait station and follow the label exactly. Pets, and birds such as ruru (morepork) and kāhu (swamp harrier), can be poisoned by eating poisoned rodents. Many households decide not to use poison outdoors at all.
• Talk to the neighbours. Let them know where the traps are, especially if they have children or a dog that visits.

When a rodent problem needs a professional

Garden traps are for keeping numbers down outdoors. If rats or mice are living inside the house, it's a different job. Signs include scratching in the ceiling or walls at night, droppings in cupboards or the roof space, gnawed wiring or pipes, or a smell under the floor. At that point, outdoor trapping won't fix it on its own, and poorly placed indoor baits can leave animals dying in walls. A licensed pest controller can find the entry points, treat roof spaces and subfloors safely, and advise on sealing gaps so they don't return.

Make it count: Predator Free 2050

New Zealand has a national goal, Predator Free 2050, to eradicate possums, rats and mustelids (stoats, ferrets and weasels) from the whole country by 2050. It sounds huge, and it is. Much of the progress so far has come from community groups. They run trap lines street by street, sharing traps, catch data and know-how, so the whole neighbourhood gets protection rather than isolated sections.

The Predator Free NZ Trust's toolkits cover identifying pests from chew cards and tracking tunnels, setting up a backyard group, and recording catches so you can see whether the work is paying off.

A simple year of backyard trapping

Season	What to focus on
Late winter to spring	Trap hard before and during nesting. Many birds lay from about September.
Summer	Keep checking. Young rats disperse and stoat numbers peak.
Autumn	Rats often move towards houses as it cools. Check traps near sheds and decks.
Winter	Hedgehogs hibernate in colder areas, but rats keep going. Keep traps baited.

Start small: one tunnel trap along the back fence and another near the compost, checked every Sunday. Record what you catch. Within a season you'll know which animals visit, and you'll probably notice more birdsong.