Western Harvest Mouse (Reithrodontomys megalotis)
This species lives in grassy areas, which can be along riverbanks, in pastures or meadows, and at edges of agriculture. They eat grass seeds, shrubs, and on occasion insects. The Western harvest mouse commonly uses runways. It is active nocturnally with its greatest activity between sunset and sunrise. They spend periods of inactivity in ball-shaped nests constructed on the surface of the ground; nests are sometimes placed beneath shrubs or debris.
Photo: Michael Hogan

Canyon Mouse Peromyscus crinitus
They have been found in rocky situations from sagebrush deserts to Ponderosa pine or fir forests. Found exclusively in steep, rocky areas such as cliffs and ravines. They build nests under rocks, in old burrows of other animals, and in piles of dead vegetation. They sleep during the day and come out to forage on seeds and vegetation during the night. 

Deer Mouse (Peromyscus maniculatus)
The deer mouse is found throughout every Oregon habitat type. It is active nocturnally; the time of onset of activity is cued by light and is remarkably precise, but does not seem to be influenced by clouds. It nests in trees, burrows in the ground, crevices in rocks, and a variety of other places. Active throughout the year during cold, wet weather, activity is curtailed aboveground, although they may be active belowground. At high elevation, they are active under the insulating cover of snow. Not shy of people, it makes itself at home in forest cabins, farmhouses, and many city houses. They eat seeds, green vegetation, insects, berries, and fungi.
Photo: James Gathany

Pinyon Mouse (Peromyscus truei)
East of the Cascade Range, it is associated with western juniper in rocky outcrops and sagebrush desert communities. They are excellent climbers and will make nests in hollows of Juniper trees. Pinyon mice are largely nocturnal. Their diet consists of seeds, nuts, berries, fungi, insects, and green vegetation, which varies by season and location no more than a quarter of its diet is plant-based. In winter they eat Juniper berries.
Photo: Sally King

Northern Grasshopper Mouse (Onychomys leucogaster)
In Oregon, Northern grasshopper mice have been found in sagebrush, juniper, and grasslands. These mice are strongly nocturnal. Light rain produces an increase in activity and heavy rain suppresses activity. While insects form the bulk of the diet, it also eats a variety of small mammals. The Northern grasshopper mouse lives in burrows underground, by either digging its own or inhabiting burrows that have been disowned. These mice have a system of multiple burrows, with each burrow serving a different function. The nest burrow is the primary area of activity during the day. The cache burrow is used for storing seeds. The signpost burrows are small and filled with glandular secretions that mark the boundaries of their territory. All of these burrows are found within a large area of territory.

Bushy-tailed Woodrat (Neotoma cinerea)
Along with the Dusky-footed woodrat, they are called a “packrat.” It is unknown why they incorporate shiny objects in their nest; it is possibly to spook predators. These nocturnal rodents can be found along rimrock canyons, cliffs, and talus slopes. They also occupy deserted buildings and mineshafts. They eat forbs, twigs, and shoots of trees, berries, fungi, flowers, and seeds.

Mostly males urinate on rocks and ledges in areas that they use leaving a white residue; this is likely a territorial marking behavior.

House Mouse (Mus musculus)
House mice live throughout most of Oregon in association with humans. House mice are usually more active at night, but within barns, warehouses, and other buildings with subdued light, they may be active at any time. Even when active, these mice usually spend most of their time behind or beneath some object and dash between the items that provide cover. They can adapt in the wild, found in riparian areas, croplands, grain fields, and pastures. In the wild, they eat a variety of things including seeds, fleshy root, and insects.

Western Red-backed Vole (Clethrionomys californicus)
It is a denizen of moist microhabitats of the conifer forest, but tends to be most abundant in closed canopy old-growth forests containing an abundance of fallen logs. The voles increase in number as the number of large rotting fallen trees increase. Their diet is almost exclusively truffles. Their year round activity is throughout the day but most activity occurs below the ground.

Long-tailed Vole (Microtus longicaudus)
Long-tailed voles live in a broad range of habitats, including dry grassland, riparian zones, subalpine meadows, and alpine tundra above timberline. Long-tailed voles build their nests above ground during the winter but in underground burrows during the summer. They primarily eat green plant material but also consume fruits and seeds. Although active mainly at night, they often are seen during the daytime in areas of heavy grass cover. During the winter, diet may consist of the inner bark of shrubs and trees

Sagebrush Vole (Lemmiscus curtatus)
Typically, this species is found in semi-arid shrub habitats with rocky soil, dominated by sagebrush or rabbitbrush mixed with bunchgrass. It occurs in grasslands if the grass is thick enough to provide cover. They eat green plant material including grasses, leaves, and seeds. The Sagebrush vole resides in colonies. They are active most of the day, year round, but their main activity is several hours before sunset, around complete darkness and around sunrise.

Common Muskrat (Ondatra zibethicus)
Muskrats are highly adapted for the aquatic environment, and although they occasionally make extensive overland treks, they usually occur in the vicinity of lakes, ponds, sloughs, swamps, marshes, rivers, and creeks. Muskrats are powerful swimmers and can stay submerged as long as 20 minutes. When swimming at the water’s surface, the muskrats head and portions of its back are out of water; with beavers usually only the head is visible.

In eastern Oregon, muskrats build large nests of vegetation and mud (beavers use wood and large branches). The nest rests on the bottom of the lake or stream, but the top of the nest may be 4 or 5 feet above water level. Muskrats are active throughout the year. They are mainly active at twilight and throughout the night.

When startled, they enter the water with a loud splash and may swim a long distance under water before coming to the surface.
Photo: D. Gordon E. Robertson