Norway Rat
Rattus norvegicus
Anatomy
Identification
Distinguishing Features
- Tail shorter than combined length of head and body
- Blunt, rounded muzzle (vs. pointed in Roof Rat)
- Small, hairy ears that don't reach the eyes when folded forward
- Heavy, stocky body weighing 200-500g
- Droppings are capsule-shaped, about 20mm long
Similar Species
- Mice are much smaller (20-30g vs 200-500g) with proportionally larger ears and longer tails relative to body size.
Biology
Lifecycle
Reach sexual maturity at 3-4 months. Females produce 3-6 litters annually, each containing 8-10 pups. Lifespan typically 1-2 years. A single pair can theoretically produce thousands of descendants in a year under ideal conditions.
Diet
Omnivorous scavengers preferring meat, fish, and grains. Require about 30g of food and 60ml of water daily. Will eat almost anything including soap, leather, and other rats. Known to gnaw through lead pipes to access water.
Nesting
Burrowing species that prefers to nest in the ground. Digs extensive burrow systems under concrete slabs, sheds, garbage piles, and foundations. Unlike Roof Rats, prefers ground level and basements. Nests are lined with shredded materials.
Signs of Infestation
Droppings
Capsule-shaped droppings about 20mm long with blunt ends. Fresh droppings are dark and moist; old ones are grey and dry. A single rat produces 40-50 droppings daily.
Gnaw marks
Teeth marks on wood, plastic, cables, and even pipes. Fresh gnaw marks are light-coloured; old ones darken over time. Can chew through concrete and lead.
Burrow entrances
Holes 7-10cm diameter under concrete slabs, sheds, compost bins, and along foundations. Look for fresh soil pushed out or worn entrances.
Grease marks (rub marks)
Dark, greasy smears along walls and runways where rats repeatedly travel. Their oily fur leaves residue on surfaces.
Sounds
Scratching, squeaking, and gnawing sounds in walls, under floors, or in ceilings, especially at night.
Footprints and tail drags
In dusty areas, look for four-toed front prints and five-toed back prints with tail drag marks between.
Where They Nest
- Under concrete slabs and porches
- In and around garbage storage areas
- Basement corners and utility rooms
- Near restaurants and food storage
- Along sewer lines and near drains
- In compost bins and under sheds
Distribution in Canada
Found in all provinces except Alberta, which maintains aggressive rat control and has been rat-free since 1950. Most common in urban centres, particularly Toronto, Montreal, and Vancouver.
Active Season
Active year-round. Indoor invasion peaks in autumn as temperatures drop and food becomes scarce outdoors. Most active at night (nocturnal). Typically stay within 30-50m of their nest.
Prevention
- Eliminate food sources - secure garbage, clean up spills, store food in sealed containers
- Remove water sources - fix leaks, eliminate standing water
- Seal entry points - gaps larger than 12mm (half inch) can allow entry
- Remove harbourage - clear debris, trim vegetation from building perimeter
- Use rat-resistant composters or eliminate backyard composting
- Install door sweeps and seal gaps around utilities
- Store firewood and lumber away from buildings
Professional Treatment
Rat control requires an integrated approach: inspection to identify entry points and harborage, exclusion work to seal access, sanitation recommendations, and strategic placement of tamper-resistant bait stations or traps. Rats are neophobic (fear new objects), making professional expertise essential for effective placement.
Get Rodent Control ServiceFrequently Asked Questions
What does a Norway Rat eat?
Omnivorous scavengers preferring meat, fish, and grains. Require about 30g of food and 60ml of water daily. Will eat almost anything including soap, leather, and other rats. Known to gnaw through lead pipes to access water.
Where does a Norway Rat nest?
Burrowing species that prefers to nest in the ground. Digs extensive burrow systems under concrete slabs, sheds, garbage piles, and foundations. Unlike Roof Rats, prefers ground level and basements. Nests are lined with shredded materials.
When is a Norway Rat most active?
Active year-round. Indoor invasion peaks in autumn as temperatures drop and food becomes scarce outdoors. Most active at night (nocturnal). Typically stay within 30-50m of their nest.
What are the signs of a Norway Rat infestation?
Droppings: Capsule-shaped droppings about 20mm long with blunt ends. Fresh droppings are dark and moist; old ones are grey and dry. A single rat produces 40-50 droppings daily. Gnaw marks: Teeth marks on wood, plastic, cables, and even pipes. Fresh gnaw marks are light-coloured; old ones darken over time. Can chew through concrete and lead. Burrow entrances: Holes 7-10cm diameter under concrete slabs, sheds, compost bins, and along foundations. Look for fresh soil pushed out or worn entrances. Grease marks (rub marks): Dark, greasy smears along walls and runways where rats repeatedly travel. Their oily fur leaves residue on surfaces. Sounds: Scratching, squeaking, and gnawing sounds in walls, under floors, or in ceilings, especially at night. Footprints and tail drags: In dusty areas, look for four-toed front prints and five-toed back prints with tail drag marks between.
How can I prevent a Norway Rat infestation?
Eliminate food sources - secure garbage, clean up spills, store food in sealed containers. Remove water sources - fix leaks, eliminate standing water. Seal entry points - gaps larger than 12mm (half inch) can allow entry. Remove harbourage - clear debris, trim vegetation from building perimeter. Use rat-resistant composters or eliminate backyard composting. Install door sweeps and seal gaps around utilities. Store firewood and lumber away from buildings.
How is a Norway Rat treated?
Rat control requires an integrated approach: inspection to identify entry points and harborage, exclusion work to seal access, sanitation recommendations, and strategic placement of tamper-resistant bait stations or traps. Rats are neophobic (fear new objects), making professional expertise essential for effective placement.
Scientific Classification
- Kingdom
- Animalia
- Phylum
- Chordata
- Class
- Mammalia
- Order
- Rodentia
- Family
- Muridae
- Genus
- Rattus
