Pet mice don't live long, but they're popular pets thanks to low cost and low maintenance needs, not to mention cuteness. In the two or three years a typical healthy mouse lives, he goes through distinct stages of development, which you can watch progress over the course of just a few weeks.
A pet mouse, even well cared for, won't typically live very long. The average house mouse lives between two and five years -- in the wild, life span averages 12 to 18 months. In the wild, a mouse is relatively small and defenseless, and makes easy prey for predators like owls, cats, foxes and others. In captivity, mice don't have to worry about predators, but they do have to worry about dangers like obesity, which can shorten their lives.
Birth and Infancy
The first stage of a mouse's life cycle lasts about a week. His infancy is marked by relative helplessness. He can't walk for a few days. When he does, he can only waddle around. A baby mouse won't have opened his eyes by the end of his life cycle's first stage, but his naked body will start to grow fur between days eight and 10 -- this marks the beginning of his next stage of life.
Bridging the gap between helpless infancy and independent adulthood, a mouse's adolescence lasts a few weeks and is marked by big personality changes. When he is about 2 weeks old, his eyes finally open. The ability to see will inspire him to get active, and he'll have a lasting burst of energy. Over the next several weeks, he'll be very active and start eating solid food -- and he'll eat plenty to fuel his growing body. He's sexually mature once he hits 5 weeks to 10 weeks old -- Female are 8 weeks to 12 weeks old before they're sexually mature adults.
The mouse has become an adult when he is sexually matured. He can live independently of other mice -- if he's a pet mouse, he needs a cage of his own to avoid an accidental pregnancy. As an adult, he may live for a few months or a few years. While it isn't common, adult mice in captivity can live as long as 6 years or so, provided they are well-fed, exercised and tended to by a veterinarian.
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