There are three kinds of rats in New Zealand, the kiore (Rattus exulans) which is the smallest, the Norway rat (Rattus norvegicus, also called the brown rat) which is the biggest and the ship rat (Rattus rattus — also called the common rat or black rat) which is the most common.
Rats eat weta and other insects, snails, frogs, lizards, tuatara, birds and bats, as well as the flowers, fruits and seeds of plants.
Kiore came to New Zealand with early Māori voyagers, while Norway rats and ship rats travelled to here on whaling ships and with early European settlers. Kiore have been outcompeted by the more recent arrivals and are now only found on several offshore islands and parts of Fiordland.
The Norway rat has a short, thick tail which is shorter than its body and it has small ears. Norway rats are particularly good swimmers and are able to swim up to 1 kilometre.
While Norway rats are found nation-wide, they are most common near bodies of water. They will dive into waterways to escape from predation and they are known to prey on crabs and mussels. Norway rats also prey on ground-nesting birds, their eggs and their chicks, such as the New Zealand dotterels and shore plover. They are able to climb trees but spend most of their time on the ground.
The ship rat has bigger ears and a tail that’s longer than its body. The ship rat is the biggest threat to wildlife because it’s a good climber and can reach nests in trees. It is thought predation by ship rats has been instrumental in the extinction of many of New Zealand’s native birds including, the bush wren (Xenicus longipes), huia (Heteralocha acutirostris), laughing owl (Sceloglaux albifacies), New Zealand little bitten (Ixobrychus novaezelandiae), and South Island snipe (Coenocorypha iredalei).
Both Norway rat and ship rats like to live near humans and can be found in houses, waterways and at tips. Ship rats will climb through cracks in walls and holes in ceilings and make their home in roofs. Norway rats will enter through a structures foundations and may dig burrows under floors. Both species are neophobic — this is the fear of novel stimuli and manifests as avoidance of new food or situations. Just because you have never seen them, does not mean they are not present!
What you can do:
- Follow our rat trapping best practice for at home and in the bush
- Rat proof your compost — food and organic waste that are improperly stored or disposed of constitutes the most significant food source for rats.
- Don’t make it easy for them — trim any trees that are up against your house. A premise is 24.2 times more likely to become infested when that structure is easily accessible to rats! Although they will cohabit with people, abandoned structures are preferred.
Read more:
- Bait consumption study shows what appeals to rats
- Secret life of urban rats revealed
- Cats vs rats (and the big ones that get away)
- Can feral cats limit rats?