Rattus norvegicus

Threats Status

Unwanted Organism

Common Name(s)

Norway rat, brown rat, water rat




Norway rats used to be widespread living in various types of habitat from coastal to subalpine areas up to 1200m. Due to the influence of competition and predation they are now mainly restricted to wetland habitats including estuaries, lakes, marshes, rivers and streams. However, commensal population occupy various urban habitats. Norway rats have a very opportunistic feeding manner. In natural environments they food consist of seeds, fruits, leaves, insects, molluscs, cetaceans and annelids. They were also reported to be feeding on eggs and killing bird chicks and rabbit young. They are also excellent swimmers (600m up to 1km). Dominant rat species (will deliberately exclude ither rodents).


Norway rats are the largest rat species in New Zealand. They have a stout body with a greyish-brown shaggy coat darkening along the back, heavy tail and relatively small eyes.

Similar Species

Norway rats may be mistaken for the other two species of rat in NZ: Ship rats (Rattus rattus) and Kiore (Rattus exulans).

Threat To Plants

Collection of seeds may alter the regeneration of these species. Prey on invertebrates and the young, eggs of birds may also have secondary effects on the vegetation due to changes in ecosystem processes.


Patchy distribution of both the North and the South Island, generally in close proximity to human settlements. Norway rat also occur on many offshore islands.


Weight: 200-300g; max. head to body length: 250mm

Year Introduced

Approximately 1770s

Reason For Introduction


Colonisation History

First introduced to New Zealand through European and North American sailing ships around 1770s. They were the first rodent to be established in New Zealand and by 1850s they were thought be common on both main islands. However the arrival of ship rats and mustelids lead to a decline in species numbers.