How Fast Rats Grow

Rats can become pregnant very quickly. The pregnant rat’s belly grows sideways, a sign that the uterus is expanding to make room for the baby. Rats have a double-pronged uterus, so they can carry many babies. Babies are born along the horns of the uterus, and some people can count the number of embryos in the rat’s belly by palpating its abdomen.

A single rat litter can have as many as 15,000 babies within a year. Rats reproduce quickly, and a single female can have up to five litters of pups in a year. Each litter increases the rat population by fourteen pups. The young rats grow from pups to mating adults in five weeks.

The fur of the baby rat begins to grow as early as two days old, although the colour may not be obvious until the first week of life. After about ten days, the baby rat will have a beautiful, plush coat, resembling a young dog. At fourteen days, the baby rat will have opened eyes and start to crawl around. The mother will feed the baby rat softer food and will put it into her nest.

A rat’s lifespan varies between two and three years, but they are not very different from each other. The female rat reaches sexual maturity in four to five weeks and will produce as many as 12 pups within their lifetime.