When is a mouse born? - briefly
A mouse is born after a gestation of approximately 19–21 days. Litters commonly consist of five to twelve offspring.
When is a mouse born? - in detail
Mice reach reproductive maturity within 5–8 weeks after birth, allowing the first litter to occur shortly thereafter. Female rodents experience a estrous cycle of 4–5 days, with ovulation occurring during the proestrus phase. After successful mating, the gestation period lasts approximately 19–21 days, varying slightly among strains and environmental conditions.
Key factors influencing the timing of parturition include:
- Strain genetics – laboratory strains such as C57BL/6 tend toward the shorter end of the gestation range, whereas outbred stocks may extend to 22 days.
- Maternal age – younger females (8–10 weeks) often produce litters at the lower gestational limit, while older breeders can exhibit marginally longer pregnancies.
- Nutrition and housing – adequate protein intake and stable temperature (20–24 °C) support optimal gestational length; stressors may induce premature delivery.
A typical birthing event occurs during the early dark phase, aligning with the species’ nocturnal activity pattern. Litters average 6–8 pups, though numbers can range from 4 to 12 depending on the aforementioned variables. Neonates are altricial: hairless, eyes closed, and incapable of thermoregulation, relying entirely on maternal care for the first two weeks.
Postnatal development proceeds rapidly. By day 4, pups develop a coat; by day 10, eyes open; and by day 14, they achieve sufficient locomotor ability to explore the nest. Weaning takes place at 21 days, after which juveniles become independent.
In summary, mouse parturition follows a predictable schedule: sexual maturity at 5–8 weeks, a 4–5‑day estrous cycle, and a gestation of roughly three weeks, culminating in a nocturnal birth of multiple altricial offspring that mature to independence within three weeks.