A rat widely found around human settlements, using sewers, warehouses, fields and other places with water and food.
Wild animals have coarse brownish-gray fur with a paler underside. The ears are small and the tail is shorter than the head and body.
A seesaw-like device opened a food box at one end when a brown rat sat on the platform at the other. In a study published in 2025, inexperienced rats reached their first successful food retrieval sooner when living with four trained companions than when living with zero or two. Seventeen of 24 inexperienced rats successfully obtained food during the experiment.
The experiment took place at the University of Bern, Switzerland, in November–December 2019. Captive wild-type females lived in six groups of six in outdoor enclosures with digging areas and shelters. Inexperienced rats were present when companions operated the apparatus and ate food when another rat opened it. Some individuals also obtained food by lifting the lid directly, rather than sitting on the platform. An alternative way of opening the box emerged alongside use of the seesaw mechanism.
An extinction-risk assessment has not been added yet.
In New Zealand, where brown rats were introduced, island biosecurity includes watching for reinvasion to protect native birds. In October 2024, DOC reported its response to one invading Norway rat on Motutapu and adjoining Rangitoto. Around 50 cameras helped track its movements. After footage showed it taking toxic bait, the absence of further camera sightings and a detection-dog search gave DOC confidence that it had died. The incident illustrates monitoring and response undertaken for island bird conservation.