Overview
The Norway rat (Rattus norvegicus), also called the brown rat or sewer rat, is the dominant rat species in Montreal and across Quebec. It is a burrowing animal that lives primarily underground but readily enters buildings through foundation gaps, utility penetrations, and damaged infrastructure. Norway rats are significantly larger and more destructive than house mice, and they pose serious health risks through disease transmission and food contamination.
How to Identify Norway Rats
- Size: 200–500 g body weight; 18–25 cm body length plus 15–20 cm tail
- Colour: Brown or grey on top, lighter grey or white underneath
- Head: Blunt, rounded nose — distinguishes it from the black rat (Rattus rattus), which has a pointed nose
- Tail: Shorter than body length, scaly, nearly hairless
- Ears: Small, close-set, covered with fine hair
- Eyes: Small, black
- Droppings: 12–20 mm long, dark brown, blunt at one end — significantly larger than mouse droppings (3–6 mm)
Biology & Reproduction
- Litters per year: 4–7
- Pups per litter: 6–12
- Gestation period: 21–23 days
- Sexual maturity: 3 months
- Lifespan: 1–2 years in the wild
- Burrowing: Excavates burrow systems 1–2 metres deep with multiple entrances and chambers
- Foraging range: Up to 50 metres from the nest
- Diet: Omnivorous — grains, meat, fish, fruit, garbage, and virtually anything organic
Health Risks
- Leptospirosis: Transmitted through urine-contaminated water or soil; can cause serious kidney and liver damage
- Hantavirus: Transmitted through droppings and urine; potentially fatal respiratory illness
- Rat-bite fever: Transmitted through bites or contact with rat saliva
- Salmonellosis: Food contamination through droppings and contact with food surfaces
- Structural damage: Gnaws through electrical cables (fire risk), plumbing, and structural materials
- Secondary pests: Rats carry fleas, ticks, and mites that can infest the home
Signs of Infestation
- Droppings: 12–20 mm, dark brown, blunt at one end — concentrated along travel routes
- Burrow entrances: Smooth, round holes (5–8 cm diameter) in soil near the foundation, under concrete slabs, and along fence lines
- Gnaw marks: Large, rough gnaw marks on wood, plastic pipes, electrical cables, and food packaging
- Grease marks: Dark smudges along walls, pipes, and beams from oil in the rat's fur
- Sounds: Scratching, gnawing, and movement in walls, under floors, and in the basement — particularly at night
- Nests: Shredded paper, fabric, and insulation in hidden locations
Prevention
- Seal all foundation cracks and gaps around utility penetrations with steel wool and hydraulic cement
- Install door sweeps on all exterior doors, including the garage door
- Store all food in airtight metal or glass containers
- Keep garbage in bins with tight-fitting lids and empty them regularly
- Eliminate outdoor food sources: bird feeders, unsecured compost, pet food left outside
- Keep vegetation trimmed back from the foundation
- Store firewood at least 6 metres from the house, elevated off the ground
- Fill abandoned rodent burrows in the yard
Professional Treatment
Professional rat control involves a two-phase approach: (1) Elimination — strategic snap traps and tamper-resistant bait stations installed in confirmed activity areas; (2) Exclusion — sealing all entry points with professional-grade materials after the existing population is eliminated. Follow-up monitoring confirms complete elimination. Do NOT seal entry points before eliminating the existing population — this traps rats inside and creates a desperate, destructive situation.