Breeding Rats FAQ
How can you tell when a female is in season?
Most female rat cycles happen every four to five days (with some exceptions) and can last for up to half a day. One of the most notable signs is that your female rat will 'vibrate' (when you rub her back she will stand very still and straight but her ears will waggle very fast and you might notice the rest of her body doing the same. She will most likely arch her bask as well). Another sign may be that the other females in the cage with her (if there are any) will try to 'mount' her. Her vagina may also look slightly more open and moist compared to its usual state (that is if you want to look there!).
What is the recommended breeding age?
Female rats tend to be sexually mature from about 6 weeks of age. However, it is strongly recommended that you do NOT breed from a female until she is at least 3-4 months old (4 months probably being about the youngest I would say).
The topmost age recommended for stopping breeding is about the year mark. Any older than that and you will be putting a lot of strain on your rat, the same as what happens in humans when they are older and pregnant. There would be a lot more risks involved health wise, for both the mother and babies.
It is also a recognised fact that the longer you leave your rat before breeding the harder it will be for her to conceive. So, if you are planning on breeding from her, it is recommended that you start breeding not long after the recommended age.
How long is the gestation period?
The gestation period in female rats is normally about 21-23 days, although this can obviously vary, like all pregnancies. Unfortunately, the female rat tends not to show a pregnancy (i.e. get fatter) until more or less the last 7 days of the pregnancy, making it hard to tell whether she has conceived or not until the last minute. She will probably also not start building a nest until nearly the last day of her pregnancy. Indeed, some rats have been known to not nest build until the actual day they are ready to give birth.
What is the duration of the mating period?
This can vary quite a lot and some say the female rat can conceive pretty quickly after being put in with a male rat. However, the law of averages suggests that the mating period can be from 9-20 hours.
To be on the safe side, you could leave the male in with the female for perhaps up to a week, increasing the chances of a pregnancy happening. Make sure they get on alright first before trying this though! And keep an eye out. Sometimes the male can get a bit too frisky and rough and may cause the female to bleed slightly - lift the male out if you think this is happening/has happened.
Are there any special considerations when looking after pregnant/nursing rats?
Like any pregnancy, be it in humans or animals, extra nutrients are needed to help chances of a normal birth and litter and cut down on any chances of illness or struggles on the mother's part. Try adding special 'small animal' vitamin supplements to her water, to try and keep her vitamins up. And perhaps a small good quality kitten food as a supplement to her diet may help keep her protein and fat levels up (although too much protein is said to be a helper in causing tumours, so I will not state just how much to give - this I leave to your discretion). Extra bread, pasta and fresh vegetables can be good for her too. Make sure she has an ample supply of her own rat food and plenty of fresh water available at all times.
Sometimes the females hormones will play a factor in how she behaves to other rats during her pregnancy. She may become more aggressive than usual, picking on the other rats she is with. If this happens it may be a good idea to remove her from the cage and put her in a second, temporary cage (let's call it the nursery, as it's so sweet!). This may be a good idea anyway, especially if your cage has bars. New baby rats are blind at birth and also very tiny, and may fall out of a barred cage. And ideal nursery would be a tank with an aerated lid.
What about the birthing procedure?
When the labour is beginning, you may notice that the female has become very restless (wouldn't you during a labour?). You may also note a small spot of blood around the urethra, which should indicate the actual birthing will come soon after.
The labour and the following birth usually only takes a matter of some hours, and everything should go to plan. However, on occasion some births DO go wrong (although this is a small percentage, it may still occur). If the birth seems to be taking a lot longer than a few hours, check the female for any signs of distress, too much bleeding (there will be some of course as each baby arrives, but it should be easy to tell if it looks like an excess), or other signs of trouble. In these cases it can often be fatal for both mum and the babies and quick expert help is required to try and save them (perhaps a good idea would be to ask around your local Vets just before the birthing is to start). In some cases like this a caesarean may be needed, especially if one of the babies has died in the womb and is blocking the birthing process, or the female's contractions have stopped or become to weak to be able to deliver by herself (just like in a human pregnancy). Unfortunately, cesareans are very stressful, complicated operations on rats, so if your rat's birthing comes to this, please be prepared that she may not survive, or the babies. Again, it is usually only a small percentage of pregnancies that show any signs of complications, so your birthing should be a normal one.
What are the general litter Sizes?
Litter sizes can of course vary, with the average said to be about 12 babies per litter. However, litters can be from just one baby up to nearly 22!! Having so many babies, of course, would be a strain on both mum and yourself, so I suppose we all pray for a normal middling sized litter!
What about keeping mum and dad together after the birth?
Because females go back into season very quickly after giving birth (normally within 36 hours), keeping dad in with mum and babies may be risky. A female rat falling pregnant so quickly after birth would probably not be a very healthy idea, as she would still be weak from her last litter and of course would still be nursing that litter when the next one comes along!
It is recommended that you give your female rat at least two months breathing space after giving birth, so that she can gain her strength and recover before gong on to have more babies.
Another consideration may be just how friendly the dad is. It has been said that sometimes dads tend to eat the young or hurt them as they see them as so much smaller. It would be safer for both mum and babies alike to leave the dad in a separate cage until they are much older and then introduce them.
Likewise if you have two nursing mums. Although some mums do tend to share responsibilities of looking after the babies (this happens a lot in the wild, where litter sizes tend to be on the big side), one mum may try to take all of the babies on herself, keeping the other mum well away from them. If they are both largish litters, this will not be good for that female's health. She probably also will not have enough milk for so many babies and more than a few may die. Other stories that have gone around are that some mums will go nuts and kill the whole litter belonging to the other female rat.
So it would be recommended that nursing mothers be kept on their own in separate cages, where it would be less stressful overall and they can get on happily with the nursing of their babies without interruptions and problems arising from other rats.
What about weaning babies and separation time?
A rat kittens are born without their fur and look like little pink kidney beans (sweet!). By the time they are about 2 weeks old they should have opened their eyes and you should be able to see their baby fur. Once their eyes have opened they will probably start to become adventurous and move around their cage (this can also happen if their eyes haven't opened, so be careful of any openings in the cage that they could fall out of).
It is recommended that you start handling the babies pretty much straight away, once things have settled down on the birthing side, as long as the mother appears to be happy with it. The handling can reduce stresses on the babies and the mother, and will also get the babies accustomed to handling and make them friendlier a lot sooner.
Make sure you have left plenty of soft foods for the mother in the cage (ones higher in protein, like kitten or puppy foods are great for her health during the birthing and feeding process). The babies will also love this and it is an easy way to introduce them to proper rat foods. Also leave a small ball of either milk or water so that as they get bigger and stop depending on the mum so much they are more able to fend for themselves. (make sure it is a shallow dish, as you don't want the babies getting stuck in it!).
Some people say that the babies should be left for about 4 weeks with their mum, however on a personal level I believe 5 weeks to be about the proper age to wean your young rats. I wouldn't leave them together any longer than this as the babies will be starting to reach sexual maturity at around 6 weeks, and so will need to be separated into boys and girls before any unwanted accidents happen.
Keep up the higher protein foods for the babies until they are about two and a half months old, then gradually reduce this to encourage them to eat the rat food.