Housemouse - Life Cycle and Reproduction

Life Cycle and Reproduction

Female house mice have an estrous cycle about four to six days long, with estrus itself lasting less than a day. If several females are held together under crowded conditions, they will often not have an estrus at all. If they are then exposed to male urine, they will come into estrus after 72 hours.

Male house mice court females by emitting characteristic ultrasonic calls in the 30 kHz–110 kHz range. The calls are most frequent during courtship when the male is sniffing and following the female; however, the calls continue after mating has begun, at which time the calls are coincident with mounting behaviour. Males can be induced to emit these calls by female pheromones. The vocalizations appear to differ between individuals and have been compared to bird songs because of their complexity. While females have the capability to produce ultrasonic calls, they typically do not do so during mating behavior.

Following copulation, female mice will normally develop a copulation plug which prevents further copulation. This plug stays in place for some 24 hours. The gestation period is about 19–21 days, and they give birth to a litter of three to 14 young (average six to eight). One female can have 5 to 10 litters per year, so the mice population can increase very quickly. Breeding occurs throughout the year (however, animals living in the wild do not reproduce in the colder months, even though they do not hibernate). The newborn are blind and without fur. Fur starts to grow about three days after birth, and the eyes open one to two weeks after birth. Males reach sexual maturity at about eight weeks and females at about six weeks, but both can breed as early as five weeks.