The game of LIFE
A pregnant female will give birth approximately three weeks after
being inseminated if she was in estrus at that moment.
Rats can't see worth a darn, but their other senses, particuarly their
senses of smell and hearing are a whole lot more sensitive than ours.
Baby rats are born deaf and blind; their eyes don't open until about two
weeks of age; but they can hear and smell well within their first week.
They will continue to suckle (drink momma's milk) for several weeks; and
are generally ready to leave home around the age of six weeks.
Their brains are most receptive before 6 weeks; this is the time the
breeder (or you, if it's your litter) should handle them frequently to get
them accustomed to the way humans smell, sound, and feel.
They should also remain with their little brothers and sisters until
at least 6 weeks of age. Rats which are removed from their litter too
soon frequently grow up to be snippy and fearful of humans.
This will also occur if the person raising them does not handle them
regularly beginning around a week after birth until 5 or 6 weeks of age.
Rats reach sexual maturity at about five weeks; but on occasion females have
been known to become pregnant by older males at less than 4 weeks of age.
Your rats will grow very fast for several months, then slow down until six or so
months. The males eventually reach a weight of about one to one-and-a-half
pounds; the females are about 30% to 50% smaller - although there are exceptions.
The average life expectancy of a domestic pet rat is between 2 and 3 years.
Some may live a little shorter period; while some have reached 4 years and
beyond. Their environment plays a big role in how long they'll live.
If they're treated well, given a big cage, some rat-mates, and a proper diet,
they tend to reward you with a longer life.
Fatty foods, cramped & filthy quarters, and lack of companionship
can cut a rat's life literally in half.