Posted: March 17, 2009, 4:30 p.m. EDT
Q: I am currently keeping four female mice and a male together in a 10-gallon habitat. The females have been together for about two weeks and seem very comfortable together, but I am not so sure about the male mouse. He is very aggressive in trying to acquire a mate, but the females just squeak and run away when he tries to mount them. I don't understand why the females are unwilling to breed. They don't bite him or fight with him. In fact, they sometimes clean him and he cleans them, but whenever he tries to mount one, they all do the same thing — squeak and run away. How can I encourage the females to mate? They are all in a 10-gallon glass habitat with pine bedding, plenty of food, a mouse wheel for exercise and wooden blocks to climb on. I keep it fairly dark throughout most of the day and the temperature is always about 75 degrees Fahrenheit. How can I help my mice successfully breed?
A: The behavior your females are exhibiting is normal. With four females in the cage, your male mouse is probably overstimulated and is trying to breed females who are not in season and are not receptive to his advances.
While successful breeding may not be an issue, your caging situation definitely is. A 10-gallon tank is not enough space to house four female mice and their litters. Mice can easily give birth to eight to 10 in their litters, and within weeks you will have more than 30 mice in a very small tank.
Male mice do not live well together and will frequently fight and can inflict serious or fatal injuries on each other, so they must be separated at 5 to 6 weeks old. Because each male mouse needs his own space, you will quickly find yourself in need of at least another dozen or so 10-gallon tanks to hold them all. If you leave just one improperly sexed male in with a large group of females, you could have hundreds of baby mice within weeks.
I strongly advise that you separate your male and contact an organization that supports mouse breeding so you can receive the education and guidance you need before you consider breeding any animal. Mice are wonderful little creatures and they make great pets, but they reproduce very quickly. Without proper education and guidance, you can quickly find yourself unable to properly care for them all.