How many pups do mice give birth to? - briefly
A typical house‑mouse litter consists of 5–8 pups, with observed ranges from 3 to 12. Litter size depends on species, maternal health, and environmental factors.
How many pups do mice give birth to? - in detail
Mice generally produce between four and twelve offspring per litter, with the most frequently reported average ranging from six to eight pups for the common laboratory strain (Mus musculus). Wild populations display a broader spectrum, often delivering five to ten young, while certain inbred laboratory lines can reach litter sizes of fourteen or more under optimal conditions.
Key variables that modify litter size include:
- Genetic background – selective breeding for high fecundity yields larger litters; strains such as C57BL/6 tend toward the lower end of the range, whereas CD‑1 and Swiss‑outbred mice routinely exceed ten pups.
- Maternal age – primiparous females (first pregnancy) usually have smaller litters; litter size peaks in females aged 3–6 months and declines thereafter.
- Nutrition and health – diets rich in protein and adequate caloric intake correlate with increased offspring numbers; disease or stress reduces litter size.
- Environmental conditions – ambient temperature, cage density, and photoperiod affect reproductive hormone cycles, influencing the number of embryos that survive to term.
- Parity – successive pregnancies tend to produce larger litters up to a point, after which reproductive efficiency wanes.
Empirical surveys of laboratory colonies report average litter sizes of:
- C57BL/6: 5–7 pups
- BALB/c: 6–8 pups
- CD‑1 (outbred): 8–12 pups
- Swiss Webster: 9–13 pups
Field studies of house mice (Mus musculus domesticus) indicate mean litter sizes of 6.5–7.5 pups, with occasional litters of up to twelve under abundant food supply.
Mice have a gestation period of approximately 19–21 days. After giving birth, females can become receptive to mating within 24 hours, allowing for a potential of five to six litters per year under laboratory conditions. The rapid reproductive turnover contributes to the observed variability in offspring numbers across different settings.
In summary, the typical mouse litter comprises six to eight pups, but genetic strain, maternal condition, and environmental factors can shift this figure upward to fourteen or downward to three. Accurate prediction of litter size therefore requires consideration of these interacting parameters.