Female rats come into heat every 5 days. When
they come in heat, it lasts overnight, so night-time is the
best time to put the male in with her. It is also best to
keep them together for around 10 days, to make sure that there
have been 2 heat cycles.
The gestation period is 21 days. During the
last few days of pregnancy, the female will suddenly look
VERY big, and you may be able to see the babies moving around
inside her. It is important not to disturb her in these last
few days. Loud noises can actually stop labour and cause problems.
Keep her in a separate cage from other rats, in a warm place
with dim light. Give her plenty of rags, shredded paper etc
so that she can make a nest for her babies.
Rats can have between 2 and 21 babies per litter.
This varies with age, diet, environment, and the number of
the female has already had. It is important not to breed a
female before she is around 5 months old, but it is also important
to breed her before she is 8 - 12 months old, if you intend
to breed her at all. After that age, if a female has not mated,
her hip bones fuse and could cause problems in a first time
pregnancy. After this first mating, a female can have litters
up to 18 months of age, but should have a rest of 4 - 6 months
between litters to recover. Remember also that males should
not be in with the females when they give birth. There is
no danger to the babies, but as soon as the mother gives birth,
she comes into heat again. Being pregnant at the same time
as having to suckle another litter is too taxing for the mother.
5 days old: basic colour visible
Black DU Berkshire kitten at 5 days old