How many litters do mice have per year? - briefly
Domestic mice usually produce five to ten litters annually, each litter comprising roughly three to twelve offspring.
How many litters do mice have per year? - in detail
Mice reach sexual maturity at 5–8 weeks, with a gestation period of approximately 19–21 days. After parturition, females can become pregnant again within 24–48 hours, allowing rapid successive breeding cycles.
Under optimal laboratory conditions—constant temperature (20–25 °C), abundant food, and no photoperiod constraints—females typically produce 8–12 litters annually. Each litter averages 5–8 pups, though litter size may range from 3 to 14 depending on strain and nutrition.
Factors influencing the number of litters per year:
- Seasonality: In temperate wild populations, breeding peaks in spring and summer; annual litters often decline to 4–6.
- Resource availability: Limited food or water reduces reproductive frequency, potentially halving the annual litter count.
- Photoperiod: Short daylight periods suppress estrus cycles, decreasing breeding opportunities.
- Health and age: Older or disease‑affected females exhibit longer inter‑litter intervals and fewer total litters.
Consequently, the maximum reproductive output for a well‑fed, climate‑controlled mouse approaches a dozen litters per year, while natural settings commonly yield half that number due to environmental constraints.