California mammals

Brush Mouse in California

Peromyscus boylii

Native to California SNR Unranked in California

Not listed as nonindigenous in California by USGS NAS; native to its California range.

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.

Brush mouse on a rocky slopeBrush mouse on oak leaf litterBrush mouse on gravel with dark eyes and large ears
Photo: Cole Wolf · CC BY 4.0Brush mouse on a rocky slopePhoto: nmoorhatch · CC BY 4.0Brush mouse on oak leaf litterPhoto: Dave Eslinger · CC BY 4.0Brush mouse on gravel with dark eyes and large ears

Brush Mouse in California, by the numbers

Common in California 34th most recorded of 241 mammals logged in California

6,916 occurrence records
34 with iNaturalist photos

Records from 2000–2026.

6,916 total records count every California occurrence from GBIF and iNaturalist; the map plots a georeferenced sample of 300; the monthly chart covers the 6,900 records with a full observation date.

When to look for the Brush Mouse in California

Most sightings fall in April to July.

6,900 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
January406
February350
March467
April596
May784
June832
July908
August528
September662
October470
November639
December258

Monthly brush mouse occurrence records (iNaturalist and GBIF) in California, 2000–2026.

Seasonality

Year-round in California, with recorded sightings peaking in April–July, with a smaller rise in September and November.

Occurrence map

Where Brush Mouse 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
San Joaquin Experimental Area 1,284
Hastings Natural History Reserve 263
Yosemite National Park 255
San Gabriel Mountains National Monument 100
Kings Canyon National Park 85
Ventana Wilderness 71
Berryessa Snow Mountain National Monument 51
Golden Trout Wilderness 45

Protected places with the most brush mouse 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
Madera County 1,496
Fresno County 1,320
Monterey County 535
San Diego County 405
Mariposa County 403
San Bernardino County 291
Los Angeles County 286
Riverside County 276
Inyo County 273
Kern County 221
Santa Barbara County 153
El Dorado County 107
37 other counties 1,150

The complete county distribution, spread across 49 California counties. Every occurrence record falls in one county, so these sum to the total. Counties from GBIF and US Census boundaries.

Brush mouse records follow California’s rocky chaparral and oak woodland. Reports gather in the southern Coast Ranges and foothills around the Los Angeles Basin, where broken slopes offer more cover than the developed basin floor.

Most records come from museum and survey work rather than casual community sightings. Reports rise through spring and early summer, with the strongest stretch around May through July. Trapping schedules and field access can shape that peak, so it shouldn’t be read as a count of mice.

Occurrence data from iNaturalist and GBIF.

Brush mouse on a rocky slope
Full species profile Brush Mouse Peromyscus boylii Size 10.7 cm4.2 in Weight 24 g0.8 oz Lifespan 1 yr View the full profile

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"