How many mice are born at a time and how often? - briefly
Domestic mice commonly give birth to litters of 5–12 offspring after a 19‑ to 21‑day gestation, enabling multiple reproductive cycles each year. Under favorable conditions, a single female can produce up to ten litters annually.
How many mice are born at a time and how often? - in detail
Mice reach sexual maturity within 5–8 weeks, after which females can produce a litter roughly every 21–28 days. The gestation period averages 19–21 days, allowing multiple reproductive cycles each year. Under optimal laboratory conditions a female may produce 5–10 litters annually; in the wild, seasonal constraints typically reduce this to 3–5 litters.
Typical litter size ranges from 4 to 12 offspring, with a median of 6–8. Factors that modify these numbers include:
- Strain or species: laboratory strains (e.g., C57BL/6) often average 6–7 pups, while wild Mus musculus may have larger litters up to 12.
- Maternal age: younger females (first parity) tend to have smaller litters; peak output occurs at 3–4 months.
- Nutrition and housing: high‑quality diet and low stress increase both litter size and frequency.
- Photoperiod: longer daylight periods stimulate more frequent estrus cycles.
Reproductive efficiency is further enhanced by the fact that females can become pregnant again within 24 hours of giving birth, a phenomenon known as postpartum estrus. Consequently, a healthy adult female mouse can generate up to 100 offspring over a two‑year lifespan when conditions remain favorable.