Oregon mammals

Norway Rat in Oregon

Rattus norvegicus

Introduced to Oregon

Oregon's Rattus norvegicus records are of an introduced species; it does not occur here as a wild native population.

IUCN Red List status

LC – Least Concern

Widespread and abundant; not at risk.

Photo: Charles J. Sharp · CC BY-SA 4.0Live Norway rat beside shallow waterPhoto: Sciadopitys from UK · CC BY-SA 2.0Brown rat crossing stones in a streamPhoto: AnemoneProjectors (talk) · CC BY-SA 2.0Norway rat feeding in short vegetationPhoto: Chuck Homler d/b/a Focus On Wildlife · CC BY-SA 4.0Brown rat standing beside rocks in an urban parkPhoto: Steve Milsom · CC0Live Norway rat walking through debris beside human structures

Photo: Charles J. Sharp · CC BY-SA 4.0Live Norway rat beside shallow waterPhoto: Sciadopitys from UK · CC BY-SA 2.0Brown rat crossing stones in a streamPhoto: AnemoneProjectors (talk) · CC BY-SA 2.0Norway rat feeding in short vegetationPhoto: Chuck Homler d/b/a Focus On Wildlife · CC BY-SA 4.0Brown rat standing beside rocks in an urban parkPhoto: Steve Milsom · CC0Live Norway rat walking through debris beside human structures

Norway Rat in Oregon, by the numbers

Occasional in Oregon 64th most recorded of 178 mammals logged in Oregon

182 occurrence records

161 with iNaturalist photos

Jul 7, 2026 Last seen in Oregon

Records from 2000–2026.

182 total records count every Oregon occurrence from GBIF and iNaturalist; the map plots a georeferenced sample of 180; the monthly chart covers the 179 records with a full observation date.

When to look for the Norway Rat in Oregon

Most sightings fall in April.

179 Oregon occurrence records (iNaturalist and GBIF) by month of year, 2000–2026. Shows when the species is recorded, not a guarantee of presence.

Monthly Oregon records (table)

Month	Records
January	8
February	11
March	12
April	22
May	9
June	20
July	18
August	17
September	16
October	17
November	22
December	7

Monthly norway rat occurrence records (iNaturalist and GBIF) in Oregon, 2000–2026.

Seasonality

Year-round in Oregon, with recorded sightings peaking in April, with a smaller rise in June–November.

Occurrence map

Where Norway Rat has been recorded in Oregon

180 records mapped · zoom and drag to explore

180 Oregon records mapped

Notable places to look

Park, forest, or monument	iNaturalist records
Cascade Range	1
Mt. Hood National Forest	1
Wapato Access Willamette River Greenway	1

Protected places with the most norway rat sightings, from the USGS Protected Areas Database plus named mountain ranges, good spots to look, not a full breakdown, so they don't sum to the total.

Where it's recorded in Oregon

County	Records
Multnomah County	87
Washington County	23
Benton County	15
Clackamas County	14
Lane County	10
Jackson County	6
Clatsop County	4
Morrow County	4
Linn County	3
Douglas County	2
Umatilla County	2
Marion County	2
5 other counties	10

The complete county distribution, spread across 17 Oregon counties. Every occurrence record falls in one county, so these sum to the total. Counties from GBIF and US Census boundaries.

Introduced Norway-rat records in Oregon are weighted toward the populated Willamette Valley and lower river corridor, with some records extending into Cascade communities. April and June stand out, but the monthly series continues through all four seasons. Occurrence reporting for a human-associated rodent is especially uneven, so these records show noticed animals rather than the species’ true abundance.

Occurrence data from iNaturalist and GBIF.

Full species profile Norway Rat Rattus norvegicus Size 15–28 cm5.9–11 in Weight 140–500 g0.3–1.1 lb Lifespan Up to 3.8 yr View the full profile

More mammals in Oregon in the atlas

Data & sources

The data and visualizations on this page draw on these open sources:

GBIFCC-BY 4.0occurrence records behind the range map, elevation, and record counts
iNaturalistCC0 / CC-BY / CC-BY-SAobservations, photos, and audio recordings
NatureServe ExplorerCC-BYthe state conservation rank
IUCN Red Listattributed factthe global conservation status
USGS NASpublic domainnative / introduced status
Natural Earthpublic domainthe relief basemap
USFSpublic domainnational-forest boundaries
USGS Protected Areas Databasepublic domainthe named parks, forests, and refuges behind "notable places to look"