Missouri Animals
Norway rat   (Rattus norvegicus)
Chordate: Vertebrate: Mammal: Rodentia: Cricetidae
Non-native mammal from Asia

Habitat: Human dwellings
Diet: Omnivorous - almost any plant and animal material
ID Features: dark brown fur
Natural History:
The Norway rat is a medium-sized rodent. It is a common resident of towns and cities. A variant of the Norway rat is the white lab rat, which is used to test chemicals in the pharmaceutical industry. It is found on all continents, and may be the next-most-successful mammal, next to humans.

Norway rat
Photo from Reg Mckenna (originally posted to Flickr as Wild Rat) [CC-BY-2.0], via Wikimedia Commons