Roof Rats and Norway Rats Behave Differently

Two species account for most home problems. The Norway rat is heavy-bodied with a blunt nose, small ears and a tail shorter than its head and body. It burrows, so look low: along foundations, under slabs and decks, beneath woodpiles, in crawl spaces and sewers. The roof rat is slimmer, with large ears, a pointed nose and a tail longer than its body. It climbs well and nests high, in attics, soffits, wall voids, palm crowns and dense ivy, travelling along fences, branches and utility lines. Identifying the species changes where traps go and which gaps matter most. Mixed populations happen, so set for what the evidence shows rather than assuming.

Reading the Sign: Droppings, Gnawing, Rubs and Noise

Rat droppings run roughly half an inch to three quarters of an inch long, far larger than the rice-grain droppings of a mouse; Norway rat pellets are blunt-ended, roof rat pellets more tapered. Gnaw marks are coarse, with paired incisor grooves, and often appear on wood edges, plastic pipe and food packaging. Rats follow the same routes nightly, leaving dark grease rub marks where oily fur meets walls, joists and pipe runs, plus smooth runways through dust or vegetation. Look for burrow openings two to four inches wide near foundations. Scratching, scurrying or gnawing overhead after dark usually points to roof rats; noise at floor level and fresh burrows point to Norway rats.

Exclusion Comes First

Trapping alone fails if the building stays open. A rat can pass through a gap of about half an inch, and will gnaw a smaller one wider. Walk the exterior slowly and look at every penetration: utility and pipe entries, dryer and bath vents, weep holes, gaps under doors, roof-to-wall junctions, soffit and fascia joints, chimney openings, crawl space vents and garage door corners. Seal with materials rodents cannot chew through, such as hardware cloth of quarter-inch mesh, sheet metal, cement mortar or copper mesh and coarse steel wool packed tight, then finished with sealant. Expanding foam alone is not a barrier; it is a filler. Fit door sweeps, screen vents, and cap chimneys.

Remove Food, Water and Harbourage

Rats stay where a meal is reliable. Store dry goods and pet food in metal or thick rigid plastic with tight lids, and stop leaving pet bowls out overnight. Bird feeders and spilled seed are a common anchor for an infestation, as are fallen fruit, unharvested vegetables, uncovered compost, pet waste and bins without lids. Fix dripping taps and irrigation leaks, and drain standing water; rats need to drink daily. Then take away shelter. Trim tree limbs and vines several feet back from the roof, cut ivy and dense ground cover away from walls, raise woodpiles and stored lumber off the ground, and clear clutter from garages, sheds and crawl spaces.

Trapping: The Part a Homeowner Controls

Snap traps remain the practical core because the result is visible and the carcass is recovered. Place traps along walls and established runways with the trigger end facing the wall, perpendicular to travel, since rats move with a shoulder against a surface. For roof rats, secure traps to rafters, joists and fence rails. Use far more traps than seems necessary, often a dozen or more for an active site, grouped in pairs a few feet apart. Rats are cautious of new objects, so pre-bait for several nights with traps unset, using a small amount of peanut butter, nut paste or dried fruit tied or smeared on the trigger. Set them all at once. Check at least daily, keep traps away from children and pets, and wear gloves when handling.

Rodenticides, Glue Boards and Handling Waste Safely

Poison is a last resort around a home. Rodents that ingest bait can poison the cats, dogs, owls, hawks and foxes that eat them, and they frequently die inside wall cavities, producing weeks of odour and flies that are expensive to reach. Where bait is used at all, the label is law: block bait secured inside tamper-resistant stations, placed where non-target animals cannot reach it. Several states now restrict second-generation anticoagulants further, so check current local rules. Glue boards are widely considered inhumane and are easily defeated by larger rats. For cleanup, ventilate first, wear gloves and a fitted respirator, mist droppings and nesting material with a disinfectant solution rather than sweeping or vacuuming dry, bag the waste, and wash up afterwards.

When to Bring in a Professional

Call a pest professional when activity continues after a few weeks of thorough trapping, when rats are in wall voids or an attic you cannot safely enter, when burrows run under a slab or into a sewer line, or when droppings and urine have contaminated insulation. A proper job starts with a full inspection, interior and exterior, roof included, and a written account of entry points and conditions found. It should cover sealing work in durable materials, monitoring, and advice on landscaping and storage, with follow-up visits. Ask what is being used and where, and ask about pet and wildlife safety. No approach guarantees permanent elimination; the gap you leave open is the one that gets used again.