How to get rid of rats. Rats are the most successful of all the world's pest animal species. They live in association with humans, scavenging on our waste and living in our homes. Rats are vectors of disease.

Identify the problem Identify the problem

There are three species of rat in New Zealand. The brown rat or Norwegian rat (Rattus norvegicus) the black rat or ship rat (Rattus rattus) and the kiore or pacific rat (Rattus exulans). The black rat is the more commonly encountered rat pest. However, the norwegian rat is increasingly common particularly in urban areas and may come to displace the black rat as it has done in the other parts of the world. It is sometimes difficult to identify which species you might have. Even a young rat can easily be mis identified as a mouse. If you want to know which species you have an infestation of try the ID Table.

The head and body of a Norwegian Rat can be up to 30cm but is normally around 20cm. The tail is usually shorter than the head and body, an adult can weigh up to half a Kilogramme, it has grey-brown fur and is lighter on the underside. Their droppings are 15-20mm long, coloured usually grey or black. The Norwegian Rat will build nests in any suitable enclosed, safe space but naturally digs burrows into the banks of rivers. It will often nest in the walls and roof voids of homes and other buildings.

The black rat is smaller and more agile than the norwegian. The tail is usually longer than the body and head. It is a better climber than the norwegian and often finds its way into buildings via poorly sealed eaves. New Zealand buildings are susceptible to infestation by black rats because of gaps under roofing in the eaves. Rats may find their way onto the roof by climbing overhanging trees. The Black Rat does not build burrows and will nest in trees or in the voids of homes and other buildings.

Other signs of rodents include hearing noises from the roof void or walls. There may be other causes. Read this article for help in identifying the cause of such sounds.


How to Get Rid of Rats

  • Bait - Place NO Rats & Mice One Feed Blocks or NO Rats & Mice Bait Blocks at strategic, safe points, inside and outside affected buildings. Strategic points include places where rats travel safely. Rats prefer to remain under cover in walls, roof voids, vegetation and piles of material. They stay close to walls and vertical surfaces where possible. Bait stations or simple lengths of pipe can encourage rats to feed on rodenticide baits in an enclosed space, they also keep bait dry and keep baits away from non-target animals.
    NO Rats & Mice Dual Action Bait & Powder is ideal for interior dry places where rodents travel such as roof spaces, ceiling voids and wall cavities. It is a bait but also contains a powder which clings to rodent paws and fur as they scurry through or over the powder. the powder is then ingested when the rodent preens killing the rat or mouse.
  • Bait Stations - For safety and effective control of rodents use NO Rats One Feed Bait Stations and NO Mice One Feed Bait Stations.
  • Trap - Snap traps can be used in conjunction with rodenticides to control rats. When rats have taken toxic bait they are more likely to be trapped and the rat bodies can be removed. Snap traps can also be used to get rid of rats in areas where rodenticides cannot be used.
  • Proof - In order to reduce populations around buildings, and before an infestation can take hold it is important to bait outside and to check for possible entry points and seal them. Young rats can get through gaps as small as the width of a pencil. Seal gaps under doors, around pipe work and cables. Cut vegetation away from roofs where it could help rodents get onto eaves and enter.

Did You Know Did You Know

Rodent pests (rats and mice) in New Zealand carry and transmit disease to humans. The transmission of disease from animals to humans is known as zoonosis.

Examples include:

Leptospirosis: Leptospira interrogans

In humans, Leptospirosis (aka Weil's disease) can cause a wide range of symptoms, including:

  • High fever
  • Muscle aches
  • Jaundice (yellow skin and eyes)
  • Red eyes
  • Abdominal Pain

Many of these symptoms can be mistaken for other diseases. In addition, some infected persons may have no symptoms at all.

How the disease spreads:

  • Eating food or drinking water contaminated with urine from infected animals
  • Contact through the skin or mucous membranes (such as inside the nose) with water or soil that is contaminated with the urine from infected animals

Salmonellosis: Salmonella typhimurium and Salmonella bovis-morblficans

Symptoms include:

  • Diarrhoea
  • Fever

Most persons infected with Salmonella develop:

  • Abdominal cramps 12 to 72 hours after infection.
  • The illness usually lasts 4 to 7 days, and most persons recover without treatment.

How the disease spreads:

  • Eating or drinking food or water that is contaminated by rat faeces.

The Black Death, otherwise known as the plague, ravaged Europe and Asia between the 14th and 17th centuries killing hundreds of millions of people. It was the black rat that transported the fleas infected with the bacterium Yersinia pestis. The fleas fed on the blood of the rats and of the people that they came in contact with, spreading the disease as they sucked. Other diseases that rats are known to transmit through their activities include Murine typhus transmitted by rat fleas.

Always wer gloves and a dust mask when entering places where rodents travel such as roof voids and sub-floors and wash hands afterwards.

The species of rodent (rats and mice) found in New Zealand are:

  • The brown rat, Norway Rat or water rat, scientific name - Rattus norvegicus
  • The roof rat, black rat or ship rat, scientific name - Rattus rattus
  • The Kiore*, polynesian rat scientific name - Rattus exulans
  • The house mouse, scientific name - Mus musculus

*Kiore are rare and now found only in Fiordland, Stewart Island and some offshore islands. They were brought to New Zealand by Maori settlers and have cultural and spiritual importance to Maori.

Rat Facts:

  • It is estimated that at any one time 10-30% of female rats are pregnant.
  • Rats eat up to 10% of their body weight in food per day.
  • Rat incisor (front) teeth are continually growing; so they gnaw to keep their teeth worn down and sharp.
  • Rats can fit their body through any gap they can fit their skull through.

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