Quick answer: Oregon has two non-native rats, and they behave very differently. The roof rats Oregon homeowners find in attics, ceiling voids, trees and ivy are slim climbers with tails longer than their bodies. Norway rats are heavier burrowers that live in crawl spaces, under decks and sheds, and along foundations. Where you find the evidence tells you which rat you have, and where to seal, trap and clean up.
Key takeaways
- Roof rats climb and nest high (attics, ceiling voids, trees, ivy); Norway rats burrow and nest low (crawl spaces, under decks, along foundations).
- The tail is the quickest field mark: longer than head and body on a roof rat, shorter on a Norway rat, according to UC IPM.
- Both rats avoid new objects, so traps and bait may sit untouched for days; pre-baiting is part of a real plan.
- In fall, dropped fruit, nuts, bird seed, chicken feed, compost and pet food pull rats toward Willamette Valley homes.
How do you tell a roof rat from a Norway rat?
Look at the tail, the ears and the build. A roof rat’s tail is longer than its head and body combined, its ears are large enough to reach its eyes, and it is sleek. A Norway rat’s tail is shorter than its body, its ears are small, and it is heavy and blunt-nosed.
OSU Extension confirms both non-native species live in Oregon: the black rat, better known as the roof rat, and the brown rat, known as the Norway rat. Both are opportunistic and adapt easily to living near people. In the crawl spaces and attics we inspect around Salem, we find both, often in the same neighborhood.
The details in the table come from the University of California’s statewide IPM program (UC IPM), with dropping shapes from NC State Extension.
| Feature | Roof rat | Norway rat |
|---|---|---|
| Weight | 5 to 10 ounces | 7 to 18 ounces |
| Build | Sleek and agile | Large and robust |
| Tail | Longer than head and body, uniformly dark | Shorter than head and body, dark above and pale below |
| Ears | Reach the eyes when folded forward | Do not reach the eyes |
| Muzzle | Pointed | Blunt |
| Droppings | About 1/2 to 3/4 inch, pointier ends | About 1/2 to 3/4 inch, rounded ends |
| Nest sites | Attics, wall and ceiling voids, cabinets; trees, shrubs and dense vegetation outdoors | Burrows along foundations and under woodpiles; basement and ground-floor areas |
| Preferred foods | Fruit, tree nuts, berries, slugs, snails, young birds and eggs | Cereal grains, meats, fish, nuts, some fruit |
| Travel routes | Utility lines, fence tops, tree limbs | Ground level, along foundations and walls |
One caution: a young Norway rat can look slim, so use the tail-to-body ratio and the ears rather than size alone.
Where do roof rats in Oregon hide inside the house?
Up high. Attic insulation, the dead space above kitchen cabinets and soffits, ceiling voids between floors, wall voids and garage rafters are the usual nest sites.
They get there the way UC IPM describes: at night, roof rats run along overhead utility lines and fence tops. Add a big-leaf maple limb resting on the roof or ivy climbing the siding, and the eaves are an easy reach. Entry is usually a gap where the roof meets a wall, an unscreened gable vent, a lifted soffit panel or loose flashing around a plumbing vent.
The evidence is overhead: scratching and running sounds after dark, droppings tucked into insulation, packed runways in attic dust and chewed wiring. Our guide to spotting rodent damage in your attic explains what to look for before you climb up.
Where do Norway rats live around the house?
Down low. Norway rats dig burrows along foundations and under sheds, decks, woodpiles, compost bins and chicken coops, and from there they work into the crawl space through a rusted vent screen or a missing access door.
Once under the house they follow plumbing and duct penetrations up into kitchen and bathroom walls, which is when homeowners first hear them. Outside, look for burrow openings with fresh dirt, worn runways in the grass along a fence, greasy rub marks on sill plates and droppings at the crawl space hatch. A dog that keeps digging at one corner of the deck is often on to something.
Because so many valley homes sit on vented crawl spaces, this is the rat problem we see most. Our guide to rodents in the crawl space covers that inspection in detail.
What attracts rats to Willamette Valley yards in fall?
Easy food close to cover. OSU Extension lists pet and chicken feed, bird seed, kitchen scraps in compost piles, dropped fruit and unsealed garbage, plus the insects that live in a compost pile that never gets hot enough.
Salem yards supply all of it in September and October. Backyard apples, pears and plums drop faster than anyone picks them up, old walnut trees and hazelnut plantings shed nuts, and ivy on fences and blackberry thickets along ditches and the Willamette River give roof rats cover and a highway. Neighborhoods along the river in Salem and Keizer, with mature oaks and maples, see the most roof rat activity we encounter.
Out toward Dallas and Monmouth, rural properties with chicken coops, feed storage, small orchards and equipment sheds give Norway rats burrow sites within a few feet of a steady meal. Harvest in the surrounding fields pushes even more rats toward buildings.
OSU Extension wildlife specialist Dana Sanchez puts the fix plainly: short-term measures such as traps or bait may reduce populations, but long-term solutions require consistent prevention. Pick up fruit weekly, store feed in metal cans with lids, feed birds sparingly, use a closed compost system and cut ivy back from the house.
How does the species change the treatment plan?
It changes where we look, where we seal and where we place equipment.
- Roof rats: inspect the roofline and attic, seal eave gaps and screen vents, trim limbs back from the roof, remove ivy, and place devices along rafters, top plates and fence tops where the runways are.
- Norway rats: inspect the foundation perimeter, crawl space and the ground under decks, repair vent screens and the access door, and place devices along the foundation and burrow runs. Burrows that stay collapsed after treatment confirm the job is done.
- Both: seal every gap larger than 1/4 inch, the threshold OSU Extension and UC IPM both use. UC IPM notes a rat can squeeze under a door with a 1/2-inch gap.
Patience is part of the plan. Rats quickly detect and avoid new objects and new foods, so UC IPM notes they often avoid traps and baits for the first several days, sometimes weeks, and that this wariness is thought to be more pronounced in roof rats. UC IPM’s answer is to leave traps baited but unset until the bait has been taken several times. OSU Extension says the same thing in fewer words: rats inspect and avoid anything new in their environment.
If you are not yet sure you have rats at all, our guide to rat droppings vs mouse droppings settles that question first.
When to call a professional
Call when you hear activity overhead or under the floor, find rat-sized droppings in the attic or crawl space, spot burrows along the foundation, or see a rat in daylight, which usually means a well-established population.
A professional rat job starts with a full inspection: roofline, attic, crawl space, foundation perimeter and the yard features that feed them. Our technicians identify the species, then our rodent control service seals the entry points with rodent-resistant materials, sets traps or tamper-resistant bait stations with the pre-baiting rats require, and returns to confirm the activity has stopped. We use EPA-registered products applied according to the label, offer family- and pet-considerate options, and tell you exactly what to expect, including any re-entry times.
Rats that have lived in insulation leave it soiled, and a crawl space with burrows often has moisture problems too. You can see everything we treat, including crawl space mold and fungus applications, on our services page. AAA Pest Exterminators has been family-owned and operated in Salem since 1997, with no long-term contracts.
Frequently asked questions
Are roof rats common in Oregon?
Yes. OSU Extension lists the black rat, the species most people call the roof rat, as one of Oregon’s two established non-native rats. In our service area they are most common in older Salem and Keizer neighborhoods with mature trees, ivy and fruit trees, especially near the Willamette River, and they almost always show up in the attic first.
Can roof rats and Norway rats live in the same house?
They can, because they use different levels of the structure. We occasionally find Norway rat burrows along a foundation and roof rat nests in the attic of the same home. Droppings with rounded ends downstairs and pointier ends upstairs are one clue. The plan then covers both the roofline and the crawl space, with pre-baited devices at each level.
Why won’t the rats take my bait or trap?
Because rats are wary of anything new. UC IPM notes they may avoid traps and bait for several days or even weeks, and roof rats are thought to be the more cautious of the two. Set traps baited but unset along an active runway, let the rats feed from them a few times, then set them. Placement on a runway matters more than the bait.
What do roof rats eat in a Salem backyard?
Mostly fruit and nuts. UC IPM lists fruit, tree nuts, berries, slugs, snails, young birds and eggs as roof rat favorites, which describes a Salem yard with an apple tree, a walnut, a bird feeder and ivy on the fence. Picking up dropped fruit, storing bird seed in a sealed can and thinning dense vines removes most of the draw.
Do rats leave on their own in spring?
No. A rat colony that found shelter and food in October has no reason to move out when the weather warms, and the burrows or attic nests are simply reused. Activity may seem quieter in summer because more feeding happens outdoors, but the population is still there. Exclusion and removal are what end it, not the season.
Pests in the nest? Don’t stress. Call the best.
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