Brush mouse

The brush mouse (Peromyscus boylii) is a type of rodent in the family Cricetidae. It belongs to the genus Peromyscus, a group of small animals often called "deermice" and related to New World mice. These mice live in the mountains of Mexico and the western parts of the United States. They are usually found in areas that are very high up, more than 2,000 meters, or about 6,600 feet, above sea level. Brush mice are interesting because they adapt well to tough, high-altitude environments, showing how animals can survive in challenging places.

Description

The brush mouse is a medium-sized mouse with small ears and a long tail. Its fur is yellowish-brown on top and slate grey underneath. The tail is mostly hairless but ends in a brush-like tuft of hair. This mouse measures between 86 to 105 mm (3.4 to 4.1 in) from head to body, with a tail length of 88 to 115 mm (3.5 to 4.5 in). It looks very similar to other mice in the same area, but you can tell it apart by its tail length, ear size, and the tuft of hair at the end of its tail.

Distribution and habitat

The brush mouse lives in areas from northern California to eastern Colorado and western Texas, and down to Baja California and southern Mexico. These mice like places with lots of shrubs and trees that are not too tall—under about 16 feet. They prefer spots with rocks and not too much grass, and they are often found near rocky areas.

Brush mice can live in places that have been affected by fires. They have been found in both burned and unburned areas, such as chaparral and pine-oak forests. They seem to like steeper slopes, like hillsides and canyons, more than flat areas.

Subspecies

There are four types of brush mice:

• P. b. boylii – northern California
• P. b. glasselli – San Pedro Nolasco Island
• P. b. rowleyi – remainder of range
• P. b. utahensis – central Utah

Density and home range

Brush mice numbers can change a lot depending on the weather. In places like coastal California, scientists found between 40 to 72 brush mice living in each hectare of land. After a very cold winter, the number dropped to just six mice per acre.

Scientists also studied where brush mice live. Male brush mice usually live in areas of about 0.72 to 1.6 acres, while females live in smaller areas of about 0.32 to 0.79 acres. These spaces can change a little bit depending on where the mice are found.

Cover requirements

Brush mice like to live in places with lots of trees and leaves. In Arizona, they are often found near rivers, with some in drier areas. They prefer spots with rocks, especially in winter and spring, and like bushes and plants more in spring too.

In New Mexico, these mice are often seen around rocks, under trees like Gambel oak and juniper, and near woodpiles. In California, they live under trees such as coast live oak and in places with lots of leaves and wet ground.

They build nests in places like fallen logs, rocks, tree holes, and burrows. Sometimes, they make nests in old mine shafts or caves using dried grasses. In California, they often choose spots with many coast live oak trees and open ground below.

Plant communities

In California, brush mice live among trees like gray pine and California buckeye. The area also has plants such as bulrushes, fourwing saltbrush, and rubber rabbitbrush, along with other plants like whiteflower currant and deerweed.

In Arizona, brush mice are found near desert willow trees and Arizona sycamore, with shrubs like evergreen sumac and skunkbush sumac. The area includes plants such as Wheeler sotol, sacahuista, and various types of grasses.

In New Mexico, brush mice live in areas with rabbitbrush and Apache plume, along with plants like fourwing saltbrush and crispleaf buckwheat, and trees such as pinyon and juniper.

Timing of major life events

Brush mice are active mainly at night. In cooler places like the Sierra Nevada in California, they do less during winter but do not sleep all winter. In warmer places such as Arizona, Texas, and northern Mexico, they are active all year.

These mice become ready to have babies between 12 to 19 weeks old. Female brush mice can become ready even faster, in about five to nine weeks. In Arizona, females born in late May or June were already expecting babies by August. In places like West Texas, Arizona, southern Utah, and Mexico, breeding can happen almost all year. But in northern California, breeding happens more in late spring and late summer, maybe because of food.

Female brush mice can have one to six babies at a time, usually three or four. They can get pregnant again while still taking care of their babies, though this might slow the babies' growth a little. Pregnancy lasts about 23 days. Females can have many groups of babies each year. The babies are ready to leave after three to four weeks.

These mice do not stay together as pairs for long, and different males may father the babies. Most live less than six months in the wild but can live up to five years when kept safely.

Food habits

Brush mice are animals that climb trees and live in bushes. They search for food like leaves and fruits in shrubs and trees. They especially like to eat acorns when they can find them.

These mice also eat small creatures like insects and cutworms, as well as many different kinds of plant seeds and fruits. They may eat parts of plants such as leaves and flowers, but mostly they prefer seeds and fruits. When there isn’t much food around, they might eat fungi. Sometimes, scientists have found bits of other small animals in their stomachs, but this does not happen often.

Brush mice have been seen storing pinyon pine seeds, which shows they might help spread seeds for some plants.

Predators

Brush mice face threats from several animals. Birds like the northern goshawk and spotted owl hunt them. Mammals such as coyotes, foxes, ringtails, martens, weasels, skunks, raccoons, bobcats, and ocelots may also catch brush mice. Snakes are another danger to these small rodents.