How many mice are born in a litter? - briefly
Laboratory mice typically produce 5 to 12 offspring per litter, with an average of about 6–8 pups. Wild species show a similar range, though environmental factors can cause variation.
How many mice are born in a litter? - in detail
Mice typically produce between three and twelve pups per birth, with the most common range falling at five to eight. The average litter size for the common house mouse (Mus musculus) is approximately 6.5 individuals, derived from numerous laboratory and field studies. Variation arises from several biological and environmental factors:
- Genetic strain: Inbred laboratory lines often yield smaller litters (4‑6 pups), while wild‑type populations can reach the upper limit of the range.
- Maternal age: Young females (first estrus) generally have fewer offspring; litter size increases after the second or third pregnancy and declines in older females.
- Nutrition: Adequate protein and caloric intake correlate with larger litters; severe restriction can reduce numbers to three or four.
- Seasonality: In temperate regions, litters born in spring and summer tend to be larger due to longer daylight and higher ambient temperatures.
- Health status: Presence of disease or parasitic load can suppress reproductive output.
Reproductive timing influences total offspring per year. Female mice reach sexual maturity around six weeks and can breed every 21‑28 days. Under optimal conditions, a single female may produce three to five litters annually, resulting in a potential annual output of 20‑40 progeny per individual.
Statistical surveys of wild populations report median litter sizes of six, with interquartile ranges of five to eight. Laboratory colonies maintained under controlled conditions often record mean values of 7.2 ± 1.1 pups.
In summary, the number of newborns per mouse birth typically spans three to twelve, centered around six to eight, and is modulated by genetics, age, diet, seasonal cues, and overall health.