Iowa mammals

Western Harvest Mouse in Iowa

Reithrodontomys megalotis

Native to Iowa S4 Apparently Secure in Iowa

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

Western harvest mouse moving through dry stems and gravelWestern harvest mouse on reddish soilWestern harvest mouse among dry leaves and stemsWestern harvest mouse beside a building threshold
Photo: Jeremiah Degenhardt · CC-BYWestern harvest mouse moving through dry stems and gravelPhoto: Jay Pruett · CC-BYWestern harvest mouse on reddish soilPhoto: Laura Castellini · CC-BYWestern harvest mouse among dry leaves and stemsPhoto: Wendy McCrady · CC-BYWestern harvest mouse beside a building threshold

Western Harvest Mouse in Iowa, by the numbers

Rare in Iowa 51st most recorded of 74 mammals logged in Iowa

338 occurrence records
6 with iNaturalist photos
Oct 24, 2025 Last seen in Iowa

Records from 2000–2026.

338 total records count every Iowa occurrence from GBIF and iNaturalist; the map plots a georeferenced sample of 300; the monthly chart covers the 332 records with a full observation date.

When to look for the Western Harvest Mouse in Iowa

Most sightings fall in December.

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

Monthly Iowa records (table)
MonthRecords
January2
February5
March23
April14
May36
June28
July8
August28
September10
October61
November37
December80

Monthly western harvest mouse occurrence records (iNaturalist and GBIF) in Iowa, 2000–2026.

Seasonality

Year-round in Iowa, with recorded sightings peaking in December, with a smaller rise in October.

Occurrence map

Where Western Harvest Mouse has been recorded in Iowa

300 records mapped · zoom and drag to explore

300 Iowa records mapped

Notable places to look

Park, forest, or monumentiNaturalist records
Dudgeon Lake Wildlife Management Area 5
Lake Anita State Park 4
Loess Hill Wildlife Management Area 3
Elk Rock State Park 2
Saylorville Wildlife Management Area 1

Protected places with the most western harvest 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 Iowa

CountyRecords
Fremont County 67
Page County 36
Marion County 29
Polk County 24
Mahaska County 21
Mills County 11
Monona County 9
Story County 8
Montgomery County 8
Johnson County 7
Linn County 7
Wapello County 7
43 other counties 104

The complete county distribution, spread across 55 Iowa counties. Every occurrence record falls in one county, so these sum to the total. Counties from GBIF and US Census boundaries.

Western harvest mice show one of the most lopsided source ratios in this Iowa dataset: 335 GBIF records against just 6 from iNaturalist, meaning trapping surveys, not casual sightings, document essentially everything known about this tiny grassland mouse in the state. NatureServe rates the state population S4, apparently secure, fitting a species that’s genuinely common in Iowa’s grasslands but rarely seen given its small size and nocturnal habits.

The handful of iNaturalist-visible records cluster loosely in spring, March carries 2 of the 4 monthly-tallied sightings, though with GBIF dominating the total record by such a wide margin, that pattern says more about when casual observers happened to encounter one than about the mouse’s actual seasonal activity.

Occurrence data from iNaturalist and GBIF.

Western harvest mouse moving through dry stems and gravel
Full species profile Western Harvest Mouse Reithrodontomys megalotis Size 11.8–17 cm4.6–6.7 in Weight 11 g0.4 oz Lifespan 1 yr View the full profile

More mammals in Iowa in the atlas

Data & sources

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