Mice are renowned for their prodigious breeding rate. A single breeding pair of mice can potentially produce thousands of offspring in a 12-month period. Female mice can get pregnant five to ten times every year, giving birth to litters of pups between three and fourteen pups. The average gestation period is only 19 to 21 days, and female mice are ready to mate immediately after giving birth to a litter. About half the mice that a female gives birth to will also be female and reach reproductive maturity after about four to six weeks.
In the wild, mice will breed during the spring, summer, and autumn seasons, but not during the winter, when their focus is on finding enough food and shelter to survive through the bitter cold. However, when they are sheltering in someone’s home and have access to all the food and warmth they need, mice will continue to reproduce throughout the whole year. The reproduction rate of indoor mice is limited by the amount of food and space available. Mice will continue to breed and grow their litters until they reach this limit.
Living indoors also significantly increases the average lifespan for mice compared to those that have to contend with the outdoors and all the dangers it contains. Outdoors, mice usually only live for around 12 months. However, indoors, mice can live for two or three years. Mice that live indoors aren’t exposed to the same dangers and environmental pressures as those living outside. Other than cats, mice don’t have to worry about predators when they’re living in your home. This leaves them free to spend their days gnawing through your possessions and feasting on whatever leftover food they can find.