Breeding

Mice are prolific breeders and have a high fertility rate. The average litter size being between 1and 32 babies, The first litter is normally smaller between 8-12.

Heat and Mating

Female mice are old enough to breed at 6-12 weeks of age. She is in heat every 4-5 days lasting for about 12 hours at a time. During this time the doe (female) is at the peak of her fertility. During the mating process the buck (male) will follow her around the cage sniffing and licking her. If the female is ready to mate she will lift up her back and and turn her tail slightly to the side. This can be repeated several times.

Gestation

Mice have a short gestation period usually lasting between 19 and 21 days. After about 15 days the female becomes noticeably larger especially over the flanks. In the later stages of the pregnancy she will need to be moved to her own cage unless you want her pregnant again. Also her behavior changes, she will be restless and builds a nest of straw, hay, or woodchips in the corner of the cage. Cardboard is also a good nesting material. She might build two nests using one as a decoy for enemies.

The Litter

Mice usually give birth late at night or early morning between 10pm and 2am The birth usually lasts for about 1/2 hour but a larger litter may take longer. Each new baby is born in an individual sac, the female removes this and bites of the umbilical cords. The babies are born naked, blind and deaf. When the birth is over the mother will clean all her babies meticulously. During this time you should leave her undisturbed for a few days, as it is not unkown for a mother to eat her own litter if she feels they are not safe.

Development Of The Young

2-3 days old The fur begins to grow
3 days the ears open
5 days the babies start moving about in circles
7 days mice start leaving the nest, mother has to take them back
8-10 days fur has grown all over and they start eating solid food
11-13 days incisor teeth start to show
12-14 days eyes open
16 days The young start jumping, this is known as the flea age
20 days mice resemble adult mice but are smaller
28 days mice need separating into male and female groups
3 months mice are fully grown adults.