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Environment

Rats

 

Rats are a risk to our homes, health and the environment. 

 

Rat in fantail nest (Photo: DOC, D Mudge). 

 

These pests eat almost anything including native species – like lizards, insects and birds and their eggs – and native seeds needed for forest regeneration.

 

They also compete with birds for food and attract larger pests, like ferrets and stoats, which eat rats.

 

As well as affecting the environment, rats can spread serious diseases that are harmful to human and animals.

 

They can also damage building materials and even create fire hazards by chewing plastic insulation on electrical wiring.

 

Although wild rats typically live just 12 to 18 months, they are prolific breeders that can produce up to 10 young every month.

 

Controlling rats

The three options to control rats are:

 

  • Poisoning
  • Trapping
  • Prevention

 

Several types of rat poison are available for purchase from the Northland Regional Council. Ratabate®, Pestoff® and Ditrac® are some of the recommended rodenticides available.

 

Eggs eaten by rats (Photo: DOC, J Innes).

 

Poisoning

Poisoning is an effective and cheap way to get rid of rats outdoors. Most rat poisons are anticoagulants and, following a single feed, the rodent will die in five to 10 days.

 

Bait stations should be used to protect non-target animals (like pets and birds) and also to shield the poison from the weather.

 

You need to use enough bait stations for the area you're trying to control – space your bait stations at 100 metre intervals.

 

Where to buy

 

Purpose built rat-bait stations keep the bait dry and safe from pets.

 

You can buy bait stations from the Northland Regional Council and most farm supply stores, or make them from a piece of drainage pipe or similar material.

 

Using bait stations 

 

  • Place four to six pellets in each bait station. Secure the bait using wire to prevent rats taking the poison away.
  • It only takes a little poison to kill a rat. Provide a single feed and don't refill it for at least a week. It takes about a week for a poisoned rat to die.
  • Remove any mouldy or wet bait.
  • For larger areas, place bait stations at 100 metre intervals along the ground or on a tree.
  • Check bait stations regularly.

 

Care with poisons

 

  • Always read the label before using poison. Make sure you follow instructions and understand the symptoms of accidental poisoning and how to treat it.
  • Put rat baits in secure places away from children, pets and stock.
  • In case of accidental human consumption, contact the National Poisons Centre on 0800 764 766 for advice.
  • Rat poison can be extremely harmful to dogs and cats. Symptoms can take several days to appear. They may include lack of appetite, lethargy, bleeding from the nose or mouth and pale gums). Vitamin K can be used as an antidote – call your vet immediately if an animal accidentally eats rat bait.

 

For more information, check out www.nrc.govt.nz/nasties

 

Trapping

Victor® trap.Trapping is best suited to small rat infestations. It is particularly good in buildings, where using poison and having rats die inside is not ideal.

 

One of the most effective and easy-to-use rat traps available is the Victor® trap – peanut butter works well as bait. These traps are available from the Northland Regional Council and some hardware stores.

 

Trap cover.Trap covers can be made out of coreflute (the material that real estate signs are made of). These keep the bait dry and prevent other animals being caught.

 

Covers should be blocked at one end and tall enough that your traps can operate properly. Traps need to be checked and baited regularly.

 

Prevention

There are some simple ways to make an environment less appealing to rats:

 

  • Remove any cover that rats can live in, including long grass or rubbish.
  • Get rid of potential food sources or store them in rat-proof containers.

 

Types of rats

There are three types of rat in New Zealand:

  • Ship rat (Rattus rattus). New Zealand's most widespread species, this rat will live anywhere food is available.

 

  • Norway rat (Rattus norvegicus). Widespread through Northland, Norway rats live near water, in buildings with suitable nesting conditions, on farms and where food is processed or stored.

 

  • Kiore or Polynesian rat (Rattus exulans). In New Zealand the kiore is only found on a small number offshore islands, but it is widespread throughout the Pacific.

 

Ship rat (Photo: DOC).  Norway rat (Photo: DOC, R Morris).

 

More information:

For further information contact Northland Regional Council biosecurity staff:
0800 002 004