How are mice born? - briefly
«Mice» undergo internal fertilization; after a gestation of about 19‑21 days the female gives birth to a litter of altricial pups. The newborns are hairless, blind, and dependent on maternal care for several weeks.
How are mice born? - in detail
Mice reproduce through internal fertilisation, followed by a short gestation and the delivery of multiple offspring. The female’s estrous cycle lasts four to five days, with ovulation occurring during the proestrus phase. Sperm are deposited in the vaginal canal during copulation, travel through the cervix and uterus, and fertilise ova in the oviducts.
After fertilisation, embryos develop into blastocysts and implant in the uterine lining within 24 hours. The gestational period for the common house mouse (Mus musculus) averages 19–21 days. During this time, rapid cell division and organogenesis produce fully formed pups that are altricial at birth.
Labor initiates with uterine contractions that increase in frequency and intensity. The cervix dilates, allowing the passage of pups through the birth canal. Each mouse typically delivers a litter of 5–10 young, though litter size may vary with strain, age and nutritional status. The mother assists by cleaning each newborn with her mouth, stimulating respiration and encouraging attachment to the nipples.
Newborn mice weigh approximately 1–2 grams and are blind, hairless and dependent on maternal milk. Their eyes open after 10–14 days, while fur appears around the same period. By the third week, the young are capable of limited locomotion and begin to wean. Full sexual maturity is reached at 6–8 weeks, enabling the continuation of the reproductive cycle.
Key physiological factors influencing successful birth include:
- Hormonal regulation: elevated progesterone maintains pregnancy; a surge in estrogen and oxytocin triggers parturition.
- Nutritional support: adequate protein and calorie intake sustain embryonic growth and milk production.
- Environmental conditions: temperature and minimal stress reduce the risk of stillbirths and maternal neglect.
Understanding these mechanisms provides a comprehensive view of mouse parturition and early development.