Norway rat
(Rattus norvegicus (Berkenhout, 1769))

This species is Introduced in the United States

States Counties Points List Species Info

Identification

Description

They usually are grayish but may vary from pure gray to a blackish- or reddish-brown. The length of the tail in a Norway rat is shorter than the length of the head and body together. The tail is dark on top and light underneath. The size often is exaggerated. The body length is up to 10 inches, and these rats average 16 inches from nose to tail.

Life Cycle

Juvenile and adult. They have moderately high reproductive rates with eight to nine pups per litter, which are weaned in about a month. Females may produce up to 20 pups. Wild rats typically live five to 12 months but can live up to three years.

Where To Look

Norway rats are burrowers and thrive in environments where there is clutter or garbage. They burrow along foundations and under debris. They are good swimmers and may enter buildings through the plumbing. These rodents commonly will follow sewers, ditches, waterways and creeks when dispersing to new areas. The home range of these rats may be as much as 50 yards (150 feet); displaced rats may travel 1 to 2 miles, however.

Chemical 

• Omnivores:  opportunistic feeder will feed on anything humans eat, they need 0.5-1 oz per day (15-30 gm) and will hoard and transport food therefore bait translocation can be a problem. They do require water daily (1-2 oz) so liquid baits can work in some situations. 
• Typical family unit dominant male, breeding female and up to 12 juveniles.  This is important to understand for control measures as typically the juveniles will be caught first and dominant males can stay hidden for long durations of time. 
• Feral rat populations live near woods and streams. In urban settings they will burrow in high vegetation areas where food is easy to find (garbage). 
• Excellent swimmers
• Commonly follow sewers, ditches, waterways, creeks when dispersing to new areas
• Displaced rats may travel 1 to 2 (4) miles
• Placement of rodent bait stations should be considered based on the location you are working in.  For example, if there is a large vacant field adjacent to the structure focus efforts around that area, rather than the front door.  
• When using, snap traps use a variety of food attractants based on observations of damage and feeding.  Dried fruits like raisins, dog treats like jerky or even nuts can draw them into a snap trap.  
• Using glue boards as a control option for this species is not effective.
• When using rodenticides experts recommend testing different types of rodent baits, as some of the grain baits might not be what the rat is searching for. 

Resources

Selected Images


Maps


EDDMapS Distribution

EDDMapS Distribution - This map is incomplete and is based only on current site and county level reports made by experts, herbaria, and literature. For more information, visit www.eddmaps.org

State Regulated List

State Lists - This map identifies those states that have this species on their invasive species list or law.

Taxonomic Rank

Domain: Eukarya
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Subclass: Theria
Order: Rodentia
Suborder: Myomorpha
Family: Muridae Illiger, 1815
Subfamily: Murinae
Genus: Rattus
Rattus norvegicus (Berkenhout, 1769)