Brush Mouse - Timing of Major Life Events

Timing of Major Life Events

Brush mice are nocturnal. Brush mice appear to limit activity during cooler months in the Sierra Nevada of California, although they are not known to hibernate or enter torpor. In southern areas, such as Arizona, Texas, and northern Mexico, brush mice are active year-round.

Brown reported that brush mice reach sexual maturity at 12–19 weeks. However, Clark reported that female brush mice may reach sexual maturity in approximately 5–9 weeks. In Arizona, females born in late May or June were found pregnant during August of the same year. In western Texas, Arizona, southern Utah, and Mexico, breeding appears to occur nearly year-round. However, in northern California, Jameson found that breeding in brush mice peaked twice each year, once in late spring and again in late summer. This result may be related to food availability.

Female brush mice carry 1–6 embryos each with an average of 3–4 embryos. Lactating females may become pregnant, although lactation may slow the development of embryos in Peromyscus species. Bradley and Schmidly reported that the gestation period of the brush mouse is around 23 days. Females may have multiple litters per year. The amount of time between litters is likely similar to other Peromyscus species and may be 25–31 days. Young are weaned at 3–4 weeks of age.

Brush mice have a promiscuous mating system. Four out of 7 litters in a California study were fathered by several males. Males and females did not share nests and mating pairs did not remain together for long periods of time.

Few Peromyscus spp. mice live longer than 6 months in the wild, but individuals may live up to 4–5 years in captivity.