Norway rat

How to recognise it

These are the features that identify a norway rat. Each one is described in words so the identification works without the diagram.

1. The tail is shorter than the head and body combined — laid back along the animal it does not reach the shoulders. This separates it from the roof rat.
2. Heavy-bodied and blunt-nosed, 200 to 250 mm excluding tail, with small ears that do not reach the eyes when folded forward.
3. Fur is coarse, brown to grey-brown above with a paler grey underside.
4. Droppings are 18 to 20 mm with blunt, rounded ends — capsule-shaped, and about three times the length of mouse droppings.

What it leaves behind

• Burrows 50 to 100 mm across in soil next to foundations, under slabs, beneath decking, and along fence lines.
• Well-worn runways with dark greasy rub marks along walls at floor level.
• Gnaw marks about 4 mm wide, and damage to wiring, plastic pipe, and structural material.

Why an infestation persists

Norway rats are ground-dwelling and burrow, so they occupy basements, crawl spaces, sewers, and the ground floor rather than the attic. They are strongly neophobic — genuinely wary of new objects in their environment, which is the opposite of mouse behaviour and means monitoring devices are often ignored for days. They pass through a gap of about 20 mm and gnaw through many materials, so exclusion has to use resistant materials.

Where it occurs

Throughout the United States, concentrated in urban areas, ports, and near waterways and sewers.

Where to look for it

• Burrow entrances 50–100 mm across along the foundation, under decking, beside sheds, and along fence lines.
• Beneath and behind refuse bins, compost heaps, and any outdoor food source including fallen fruit and spilled birdseed.
• Basements, crawl spaces, and the void under a ground floor, following greasy rub marks along the wall base.
• Drain runs and inspection chambers — a broken sewer lateral is a common and frequently missed route into a building.
• Under a garden shed or timber decking with an open void beneath.
• Gnaw damage on plastic pipe, cabling, and door bottoms, which indicates a route in current use.

When you see it, and why

Populations build through summer on outdoor food and press into buildings in autumn as that food disappears and temperatures drop. Activity is nocturnal, so daytime sightings are worth noting: they usually indicate a population large enough that competition is pushing individuals out of cover, which is a sign the problem is further advanced than it looks. Burrow activity is easier to read after rain, when fresh spoil shows clearly.

What getting the identification wrong costs you

Separating this from the roof rat determines where you look and therefore whether you find anything. A Norway rat is a ground and burrow animal — the basement, the foundation line, the drain. A roof rat is an overhead animal — the attic, the roofline, the branches. Searching an attic for a Norway rat, or a basement for a roof rat, produces a fruitless inspection and the conclusion that there is no problem. Lay the tail back along the body: shorter than head and body means Norway.

What a professional actually does

The durable contribution is a survey that finds every burrow and every entry point, including the drainage system, followed by proofing in materials a rat cannot gnaw through. A CCTV drain survey is worth asking about where a building has recurring rat activity with no visible surface route, because a damaged lateral is a common cause and no amount of surface work resolves it. A service that removes animals without proofing will be needed again.

What it costs

Judge the quote on the proofing, not the visits. Removal without exclusion is an ongoing charge with no end date, and a property adjoining a neglected neighbouring site will need it indefinitely. Where a drain defect is the cause, the meaningful cost is the drain repair, which is a drainage contractor's work and should be quoted separately.