Mouse Fancier

Breeding - Under Construction
When you decide to breed your mice, you should first choose the parents wisely. Make sure that their colors will compliment each other, and not produce any lethal genes or unwanted babies. For example, if you wanted to get brindle pups, you wouldn't want to breed two self black mice who each had a brindle parent. If you don't know why, then read the genetics section. Also make sure the female is over 4 months and under 7 months for a first litter. Try not to breed a female back to back, if it is at all possible. This is not good for the female or the litters. Please remember, before you ever breed your mice, that mice usually have anywhere from 4 - 10 babies. Its not uncommon to get litters of 12. My average litter size was about 9 pups, but I had one mouse who had 2 litters of 15 and 1 litter of 16!

Pregnancy
Once you have chosen the desired pair and mated them, its time to start preparing yourself for your new litter. Gestation is approximately 21 days. This time frame varies from female to female, so its best not to wait until the 21st day to prepare the cage for your new arrivals.

As soon as you have bred the new female, you will need to make a few very important decisions. You should first decide whether or not to leave the father in. If you want to be able to house some of the male offspring with him, then you will need to leave him in with mom. If you don't want to jeopardize the health of mom and the litter, then take him out. Do not put dad back in after the babies are born. He will, most likely, kill the babies and impregnate mom again.

The next decision you should make is whether or not mom will have a nursemaid. If you're going to leave the father in, then this is not necessary. A nursemaid is another female mouse (whether pregnant or not) who will help the new mom with her responsibilities. I have heard that female mice possess an ability called sympathetic lactation. This means they will produce milk for offspring that is not their own even if they are not pregnant. I've found this to be true for the most part. Its important to remember that not all female mice make good nursemaids.

Usually, female mice can handle the litter on their own, but I have had some cases where a nursemaid was required. I had one line of females (3 generations) that would get sick after having their babies. The mother would become infertile or die from the stress. Where I live, there is not an abundance of mice at all. So I tried to breed this out of the line. I found that having a nursemaid in the cage with the females would eradicate the problem for that litter. Of course, I've had nursemaids who smothered the babies, bit off all their tails, and just killed them for whatever reason. If you use a female who is a good brood doe with her own young, then you shouldn't have any problems Try not to leave in really young females, as they may cause more harm than help.

Another important decision that should be made immediately is housing. If your mouse is currently being housed in a wire cage, then you may want to consider moving her into an aquarium with a lid, for several reasons. Wire cages make for easy escapes with young mice, they can be very drafty in the winter months, and, if they have a wire bottom, the babies could fall through the wire and starve to death.

Now that you have made the important decisions, its time to fuss over mom a bit. Mom will need to have her food increased over the next few weeks. She will begin to show signs of pregnancy around the 14th day. It is at this time (14 days), that you will want to give her a nest box and nesting material. Do not give mice any kind of cotton or raveling fabric for nesting material. Babies limbs can easily get tangled in this. The best types of bedding are Timothy Hay, toilet paper, or shredded paper (make sure there's no ink on the paper). Make sure that the nest box is away from any areas where you may have to stick your hand during the first few days after the babies are born (especially if the female is not very tame). Also be sure your mouse has a constant supply of food or water (to prevent unnecessary cannibalism).

When the mouse is noticeably pregnant, it is best to not to pick her up, as you could injure the babies inside her. When she begins having the babies, do your best not to disturb the cage. If you accidentally lift the nest box while she's in labor, don't panic. Just replace the nest box, and go about like nothing is unusual. If you seemed stressed, it may stress her more.

Here are some photos of pregnant does and various stages of pregnancy:

Pictured: Pregnant Variegated Black Fuzzy Hairless
Copyright © A. Hamilton 2006
Owned by A. Hamilton/Bred by Timiae Harper

Pictured: Pregnant Satin Agouti
Copyright © A. Hamilton 2006
Owned by A. Hamilton/Bred by Timiae Harper

Pictured: Pregnant Agouti
Copyright © A. Hamilton 2006
Owned by A. Hamilton/Bred by Timiae Harper

Pictured: Very Pregnant Longhair Broken Black
Copyright © A. Hamilton 2007
Owned by A. Hamilton/Bred by Kelli Boka

Pictured: Slightly Pregnant Recessive Yellow
Copyright © A. Hamilton 2007
Owned by A. Hamilton/Bred by Robin Anderson

Ok, if worse comes to worst, and your female begins eating her babies, the best advice I can give is to let it be. The mouse is not killing her babies to be mean. If she has plenty of food and water and nothing upset her during labor, then there is probably something wrong with the babies. There were many times that I tried to save the babies by fostering them onto another mother, to only result in the babies dying a few days later anyway. Its possible that the mother is only culling a few, and if you take her other babies away, you risk losing the whole litter. Its a terrible feeling to think that you let them die, but it is probably better for them in the long run.

There are some instances when you should foster the babies onto another mother. You should try to foster the babies onto another mother if you see that the mother is ignoring the babies and not taking care of them, if the mother dies somehow or another, or if she is killing them in a senseless way. I once had a Dwarf Hamster who would pick her babies up and run around with them, then when she got thirsty, she would drop them in the water bowl while she took a drink. The problem was she wouldn't get them back out again.

If you've made it through pregnancy and you have a beautiful healthy litter, pat yourself on the back and head to the next section.

Life Stages

Ah... the joys of parenthood. When your babies are first born they will be blind, deaf, and very pink (hairless). They squeak constantly and drive their wee mothers insane! Don't worry, though. It will get much more fun as it progresses.

Most people will tell you not to pick up the babies until the 3rd or 5th day. I agree with this if you are inexperienced and your females are untrusting of you. When I raised mice, I knew which females were safe to mess with that first day (which was pretty much any mouse that I bred and raised myself). On the first day, I would always count them, see what color their eyes were, and sex them (which most people can't do on day 1 anyway). That way I would have a pretty good idea of what I was dealing with. Week 1 is all about waiting. You can get an idea of whether you have dark or light-colored mice and black or pink eyed mice. If you have a pretty good concept of the parent's genetics, then usually you can tell by the end of the week what varieties you're dealing with.

Here are some photos of mice litters from Week 1:

Pictured: Day 1
Copyright © A. Hamilton 2006
Owned/Bred by A. Hamilton

Pictured: Day 3
Copyright © A. Hamilton 2006
Owned/Bred by A. Hamilton

Pictured: Day 6
Copyright © A. Hamilton 2006
Owned/Bred by A. Hamilton

Pictured: Day 7
Copyright © A. Hamilton 2006
Owned/Bred by A. Hamilton

Week 2 isn't much better than week 1. At least, during week 2 you know what colors you have for sure. Usually by the end of week 2, the babies have their eyes open, and they may begin crawling out of the nest.

Here are some random litter photos of Week 2:

Pictured: Day 8
Copyright © A. Hamilton 2006
Owned/Bred by A. Hamilton

Pictured: Day 9
Copyright © A. Hamilton 2006
Owned/Bred by A. Hamilton

Pictured: Day 11
Copyright © A. Hamilton 2006
Owned/Bred by A. Hamilton

Pictured: Day 12
Copyright © A. Hamilton 2006
Owned/Bred by A. Hamilton

Week 3 is probably the most fun. This is what mouse fanciers call the "hopper" stage. This is the week where your babies act like a bunch of 5 years old who have had about 3 cups of pure sugar. Well, they act like that when you try to hold them. It is best to hold hoppers over and slightly down in the cage at this point. I think the majority of the escapees I've ever had were hoppers who jumped out of my hands. I even accidentally killed a beautiful satin blue brindle female hopper one time when she got away. So I think its best to take extra precaution during this time, and to not let other people mess with your hoppers.

Here are some random photos of 3 week old mice:

At some point during nursing, mom will suddenly start putting weight back on. Most people who are new to mice freak out, thinking she is pregnant again. I'm not real sure why mom puts weight back on (maybe because she's not getting enough exercise). However, unless you left dad in with the litter, there shouldn't be any reason for concern.

Weaning
During week 3 and 4 your babies will begin coming out of the nest to eat with mom. You will notice because mom won't look so stressed anymore (haha). Its probably not wise to separate your babies at this point, because some will not be fully weaned yet. It is also a good idea to offer them food on your hand to try and socialize them better at this stage. You'll want to make sure that they know how to use the water bottle also (and can reach it) .

Sexing

Eventually, you will have to do this. Unless you want 531,441 mice running around in a matter of months ("I think its time to get a bigger tank, Edna"). Surprisingly (to myself) after searching through my thousands of mouse photos, I realized I had never specifically taken mouse genatilia comparision shots. However, below find pictures of female, male, and hermaphrodite genatilia (which I just happened to have taken for other reasons):

I think one of the best ways to tell is when the babies are still fuzzy. Right before they get their thick coats in (the eyes will still be closed), their little bellies will still be pink and hairless. Usually you can tell them apart at this point (unless they're all the same color). Flip the mice over and look for nipples on their bellies (they're tiny, now). This is a great trick for people new to the fancy. If you can, at least, get the sex of one mouse by this method, then later you can compare that mouse's genitalia to the others to determine the sex of the rest. Also, check them everyday for a few days in a row, especially if one of the mice is smaller than the others. Some babies will mature slower than the rest.

If you missed your window of opportunity in the fuzzy stage, then you can tell the gender by the spacing between the reproductive organ and the anus. Males will have more room between their reproductive organ and anus, and females will have less spacing. Also, after about 5 weeks, males usually have testicles the size of an unshelled peanut (which is a dead giveaway). Be careful, though! They can retract them into their body making them look like a female.

Separating
After you've weaned and sexed your babies, you will want to separate the males and females. Females can stay with mom, and males can be put in a cage together, temporarily (and in some cases permanently). You will want to begin separation sometime between 4 1/2 and 6 weeks. Usually the best time is 5 weeks, to make sure you don't have any accidents. Just remember, in some cases, male mice can mature as early as 3 1/2 weeks. Keep a close eye on things, and if your males seem like they are maturing fast (which is not all that common), then separate them sooner.

If, after about 8 weeks, any of the male mice begin fighting (if there is bloodshed and one of the mice is living a poor existence), you will want to remove the more territorial males (always remove the bully - not the victim). You may even want to consider not breeding from the more territorial males. Nine times out of ten, if you cull out any extremely territorial males from your breeding stock, you will have a much more enjoyable experience. If, for some reason, you can't cull a male, then try to breed him to a docile female (preferably one who has a father with a good temperament).