California mammals

Black Rat in California

Rattus rattus

Introduced to California

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

IUCN Red List status

  1. LC
  2. NT
  3. VU
  4. EN
  5. CR
  6. EW
  7. EX

LC – Least Concern

Widespread and abundant; not at risk.

Black Rat in California, by the numbers

Common in California 49th most recorded of 241 mammals logged in California

2,180 occurrence records
1,524 with iNaturalist photos

Records from 2000–2026.

2,180 total records count every California occurrence from GBIF and iNaturalist; the map plots a georeferenced sample of 300; the monthly chart covers the 2,173 records with a full observation date.

When to look for the Black Rat in California

Recorded year-round, with no strong seasonal peak.

2,173 California occurrence records (iNaturalist and GBIF) by month of year, 2000–2026. Shows when the species is recorded, not a guarantee of presence.

Monthly California records (table)
MonthRecords
January191
February121
March171
April171
May181
June195
July190
August214
September177
October228
November195
December139

Monthly black rat occurrence records (iNaturalist and GBIF) in California, 2000–2026.

Seasonality

Year-round in California, with no strong seasonal peak in observations.

Occurrence map

Where Black Rat has been recorded in California

300 records mapped · zoom and drag to explore

300 California records mapped

Notable places to look

Park, forest, or monumentiNaturalist records
Channel Islands National Park 27
Golden Gate National Recreation Area 12
Santa Monica Mountains National Recreation Area 7
China Camp State Park 5
Cleveland National Forest 2
Crystal Cove State Park 2
Monterey State Historic Park 1
Mount Sutro Open Space Reserve 1

Protected places with the most black 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 California

CountyRecords
Los Angeles County 441
San Diego County 335
Alameda County 172
Contra Costa County 113
Orange County 110
Santa Clara County 107
Riverside County 100
Ventura County 91
Humboldt County 79
Santa Barbara County 79
San Francisco County 78
San Mateo County 71
38 other counties 404

The complete county distribution, spread across 50 California counties. Every occurrence record falls in one county, so these sum to the total. Counties from GBIF and US Census boundaries.

Black Rat records in California need an origin check because the species is introduced, domestic, or tied to managed herds.

Reports center on localized California records that shouldn’t be read as a continuous native range. They show where people have documented the species, and they don’t rank California’s best habitat.

Records don’t show a strong seasonal peak. Reports spread across the year, but their totals don’t measure population size.

Occurrence data from iNaturalist and GBIF.

More mammals in California 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"