Rats: know your pest!

Rats (Rattus spp.)

Identification and habitat
There are three rat species present in New Zealand, the Norway rat (known as the water or brown rat), the ship rat (known as the black rat) and the kiore rat.
The kiore rat is absent on Banks Peninsula.

The Norway rat has a short, thick tail, which is shorter than its body, and small ears. The ship rat has bigger ears and a tail that’s longer than its body.

Habitats
Both Norway and ship rats are found nationwide. Can live in most habitats but are frequently found near human habitation where there is more food to scavenge. Norway rats are more prevalent near water sources. Ship rats often live in houses roof spaces if not secured.

Behaviours

• All rats are neophobic, meaning they do not like new things in their environment and will leave them be until they have been present for a long time.
• Norway rats are great swimmers and can swim up to a kilometre if needed, but not as good at climbing, but can climb some trees.
• Ship rats are excellent climbers, and some will live almost their entire lives in the canopy of trees and not descend to the ground.
• They are omnivores and will eat a wide variety of foods including both plant and animals.

Threats – why are they a problem?

• Both are carriers of leptospirosis, a bacterial disease that is spread in the urine of rodents and causes significant illness and is sometimes fatal.
• Both are agricultural pests. They eat and contaminate stored animal food, human food and can cause significant damage to infrastructure like chewing through cables and wooden supports.
• Their populations can boom in times of good food production, which leads to more rats. After the food source decreases, rats will prey switch to our native species like birds, eggs, lizards and invertebrates.
• They are food competitors against many native species, meaning they will eat much of the berries, flowers and invertebrates, other species need to survive.