How do Japanese mice reproduce? - briefly
Japanese mice breed continuously, with females becoming receptive every 4–5 days and mating shortly thereafter. Gestation lasts roughly 20 days, yielding 5–8 offspring per litter and permitting multiple litters each year.
How do Japanese mice reproduce? - in detail
Japanese mice reproduce through a seasonal breeding cycle that aligns with temperature and photoperiod. Males reach sexual maturity at 5–6 weeks, develop enlarged testes, and produce sperm continuously once mature. Females become fertile after 4–5 weeks, entering estrus approximately every 4–5 days during the breeding season.
Mating occurs after the female emits estrus pheromones; the male initiates copulation with a brief mounting sequence lasting 30–60 seconds. Successful intromission results in the transfer of a sperm plug that prevents subsequent matings for several hours.
Key reproductive parameters:
- Estrous cycle: Proestrus (≈12 h), estrus (≈12 h), metestrus (≈12 h), diestrus (≈36 h). Cycle repeats only when environmental cues are favorable.
- Gestation: 19–21 days, with embryonic development proceeding through implantation, organogenesis, and fetal growth stages.
- Litter size: 4–8 pups on average; litter size correlates with maternal age and nutrition.
- Weaning: Pups detach from the dam at 21 days, achieving independence and sexual maturity within 6–8 weeks.
- Breeding season: Peaks from late spring to early autumn; reduced daylight or low temperatures suppress estrus in females.
Hormonal regulation involves rising estradiol levels triggering the LH surge that induces ovulation, while progesterone maintains pregnancy. In males, testosterone drives spermatogenesis and aggressive courtship behavior.
Environmental factors such as food abundance, population density, and stress modulate reproductive output. Laboratory colonies maintain constant temperature (22 ± 2 °C) and a 12 h light/dark cycle to ensure regular breeding, whereas wild populations display fluctuations in litter size and timing in response to seasonal resource availability.