Several females reside in the territory of the male, hence the loose colonial organization. Breeds year-round, with peaks in early spring and late summer. Gestation period is 19-21 days. Females breed at 8 wk. Competitors include introduced Norway and black rats and many rodents.
House mice are subordinant to harvest mice and meadow voles.
Abundance in agricultural lands probably limited by the availability of cover. Epizootic outbreaks probably keep densities below maximum level afforded by food resources. House mice are host to a variety of parasites. Serv., Lassen Natl. For., Susanville, CA. 255pp.