Mice are typically thought of as the most successful invasive species of mammals. This is because they can easily invade the home and breed in large numbers in a short amount of time. In fact, newborn mice are typically ready to mate within the first 6 weeks. Some mice even begin to show signs of estrus (being in heat) within the first 25 days.

Mice can have between 5 to 10 litters in a year, each litter having 5-12 offspring. Most mouse litters have about 6-8 babies. In addition to the relatively large litter numbers, mice can be ready to mate as soon as they give birth to a litter, meaning that a second litter can be born in as little as 3-4 weeks after the first. Let’s learn more about mouse reproduction.

How many babies do mice usually have?

For most homeowners, a mouse infestation is their worst nightmare. Not only are mice larger than most other rodents, they’re also likely to cause more damage to the home as they look for food and shelter. Mice have also been shown to spread harmful diseases that can significantly affect your health.

Mouse babiesAmong the biggest concerns with mice is their ability to reproduce in large numbers and in a short amount of time. All it takes is for a pregnant female to seek shelter in your home and things will get complicated quite quickly. The answer to the question how many babies do mice have is not quite straightforward. The actual number of offspring a mouse will have will depend on the availability of breeding partners and how many litters they will give birth to in a single year.

Because it is estimated that a female can birth about 25-60 offspring in one year, the number of children the mouse will have will depend on how long it will live after attaining fertility.

A mouse that is outdoors will typically live for about a year. However, their lifespan is significantly increased when they seek shelter in your home. An indoor mouse can live for anywhere between 2-3 years, remaining fertile during most of this time. This means that a single female living in your home until death can birth between 50-180 offspring over its lifespan. Get more information on how long do mice live by clicking here.

Note
Mice are capable of having 5 to 10 litters in a year, with each litter having about 6-8 offspring. Theoretically, this means that a single female can have up to 80 offspring in one year. In more practical cases however, most females will birth about 25-60 offspring in one year. Each female offspring that is given birth to can begin to have its own litter in 4-6 weeks, further increasing the population in a short amount of time.

Mice that live indoors are capable of breeding all year round. They can seek warm shelter within your home to have their litter and prepare for the next time they will breed. On the other hand, outdoor mice are typically not capable of breeding during the winter due to the extreme weather conditions. Do mice hibernate? Click this to know.

Mouse Life Cycle

Mouse Life Cycle

How many mice are born in a litter?

Mouse litters typically lie between 5-12 in number. Mice have large litters because while out in the wild, there are many dangers that their vulnerable young may face. This often causes only a few of the litter to grow into successful adults. When mice pups are born, they are furless, blind, and defenseless.

The mother needs to nurse and protect the offspring for 21 days before they are able to wean. The early days of mice are typically characterized by rapid progress.

This often includes:

  • Ears growing and opening by the 4th day.
  • The fur begins growing on the 6th day and is fully developed by the 10th day.
  • Eyes fully opening on day 13 or 14.
  • Weaning occurs on about the 21st day.

Newborn mice

The number of mice that will be born in a single litter will depend on the health of the mother before and during the pregnancy. This will largely be determined by the availability of food and shelter in the surrounding environment. That is why mice in your home are likely to have larger litters if they have enough to chew and feast on a regular basis. Are mice dangerous? Click here to find out the possible effects of mice on your home.

How often do mice mate, and how quickly do they breed?

Mice can mate between 5-10 times a year. A female is typically ready to mate as soon as she gives birth to a litter, meaning that a new litter can be on the way in as little as 25 days after the first one. Once a male and female mate, it will take about 3 weeks for the litter to be born. The male mice will typically want to ensure that it is only their own offspring that survive in their territory.

Mice can have anywhere between 25-50 offspring in one year.

Small miceTherefore, they may kill offspring that they suspect not to be theirs so they can ensure that it is only their genes being passed on. Mice will mate about 5-10 times a year, with a lifespan of 2-3 years in your home. A single male or female may end up mating about 15-25 times during its lifespan.

How long does it take for mice to reproduce?

Considering how fast mice reach maturity, how large their litters are, and how often they mate, mice reproduce and multiply relatively quickly.

  1. Imagine a single female from the time they are born. They take about 3 weeks to fully develop their fur, eyes, ears, and other body organs.
  2. In about 6 weeks, they are ready to breed.
  3. Upon successful breeding, they give birth in about 21 days to 6-8 offspring (sometimes more).
  4. After a nursing period of 21 days, they are ready to breed again.
  5. The mouse numbers are compounded by the fact that their offspring are also ready to mate in about 6 weeks after they are born.
  6. By the time the original female is at the end of their lifecycle, they have typically witnessed 2-3 generations.

Mice infestation

Mice are capable of having many offspring because they have relatively short breeding periods and they give birth to many children in a single litter. If they end up indoors (such as in your home), they can live for longer (2-3 years) and give birth to more offspring during that time. This means that a mouse infestation can rapidly spread in your home as long as the rodents have adequate food and shelter.

You can find further details of Mice Control here.