How do mice reproduce? - briefly
Mice breed continuously, with females cycling every 4–5 days; during estrus a male mounts, copulates, and transfers sperm that fertilizes the ova. Gestation lasts 19–21 days, producing litters of 5–8 pups that reach sexual maturity in roughly 6–8 weeks.
How do mice reproduce? - in detail
Mice reach sexual maturity at 5–8 weeks for females and 6–10 weeks for males. Female cycles are estrous, lasting 4–5 days, with ovulation occurring on the night of estrus. Mating typically happens in the early dark phase; the male mounts, grasps the female’s neck with his teeth, and copulates for 3–5 minutes. Sperm are transferred to the vaginal canal, travel through the cervix and uterus, and reach the oviducts where fertilization takes place.
The fertilized egg implants in the uterine wall within 24 hours. Gestation lasts 19–21 days. During this period, the placenta supplies nutrients and removes waste, while maternal hormones (progesterone, estrogen) maintain uterine environment. Litter size averages 6–8 pups, but ranges from 3 to 14. Newborns are altricial: hairless, eyes closed, and dependent on maternal care. The mother provides warmth, cleans the pups, and supplies milk rich in proteins and antibodies.
Pup development proceeds rapidly. Eyes open at 10–14 days, fur appears at 2 weeks, and weaning occurs around 21 days. After weaning, juveniles achieve sexual maturity within 4–6 weeks, allowing successive breeding cycles. Males become sexually active shortly after puberty, while females may experience a postpartum estrus, enabling immediate re‑mating.
Key physiological controls include:
- Gonadotropin‑releasing hormone (GnRH) from the hypothalamus, stimulating pituitary release of LH and FSH.
- LH surge triggers ovulation; FSH supports follicular development.
- Prolactin promotes milk production during lactation.
- Oxytocin facilitates uterine contractions at parturition and milk let‑down.
Environmental factors such as photoperiod, temperature, and population density can modify reproductive timing, but the core biological sequence remains consistent across laboratory and wild populations.