Mice | Breeding
Filed in Small Animals, Mice
Sexually mature mice must be properly paired to breed successfully. A single male mouse may be included in a cage with one or more female mice without difficulty. Including more than one male mouse in this situation invites fighting between them. Sexually mature mice exhibit a prominent scrotum. Sexually mature female mice exhibit a prominent double row of nipples.
Female mice should not be bred before 50 days of age. They are continuously polyestrous, which means they come into heat at regular intervals of four to five days throughout the year, unless they are pregnant or nursing.
The period during which the female is receptive to the male is about 12 hours in duration, and usually occurs at night. Females can come back into heat within 14-28 hours after giving birth to a litter. This is called a postpartum estrus, which means that they can be nursing a litter and pregnant at the same time.
Pregnancy lasts an average of three weeks, but can be extended as much as 10 days longer if a pregnant female is suckling a previous litter. Litter sizes average 10-12 pups, thought it is not unusual for a female's first litter to be smaller in number. Litter sized decrease as breeding females age. Do not disturb mice for the first two to three days after giving birth. Pups are weaned at about three weeks of age.
Irving Street Veterinary Hospital (San Francisco, CA) materials were used as an information source for this article.