Breeding Rats

If you have made the decision to breed a litter with your rats, there are a few things it is prudent to consider prior.

Choosing the right pair

Photo of two adult rats looking out from inside a cage
Careful selection when breeding is important

We believe that considering the widespread health problems that Australia’s captive population of rats already has, it is very important to choose potential pairs very carefully.

Consideration should be given primarily to health and temperament and to a lesser extent conformation and size, then to the aesthetic factors of colour, markings and coat.

Rehoming the ratlets

When working out colours, markings and coat types that you expect to get from your chosen pair, ask yourself whether they are popular in your area. A mixed litter with many colours, coat types and markings will be easier to rehome for example, than a full litter of black hoodeds.

Rats on average have between eight and thirteen pinkies, however the range can be anywhere from one to twenty! You will need to find homes for the babies that you don’t keep yourself. Advertising your litter prior to breeding the parents is a great way to get a waiting list going, so that when you finally have your babies you know that they already have homes waiting for them. If you do not receive any interest from your advertisement, you know that if you go ahead with the litter you may have to keep all the ratlets yourself and you can then make an informed decision.

Recommended breeding age

Picture of three rats hanging out from the door of their cage
Waiting until a doe is properly mature is recommended

We breed our does for the first time between six and ten months of age, and each doe only ever has two litters in her life, with most only ever having one. Although it is physically possible for does to have a litter as young as five weeks of age, we like to wait until the doe is fully mature at six months. This is because a mature doe is better able to cope with the physical demands of breeding a healthy litter of babies, and also because we have then had at least six months for any potential health problems to present themselves. Of course health problems can still occur at any time, but generally if rats are going to have a life of myco related illness, they have shown some signs of this by six months of age.

The maximum age for breeding does is variable. A first litter should really be done by 12 months of age. After twelve months, there is a greater chance that complications with the birth will be experienced. That said, older does are still capable of raising a healthy litter. Does over fourteen months will generally take longer to fall pregnant due to decreased fertility, will have smaller litters and take longer to recover from raising the litter than a doe in the optimum age bracket for breeding of six to twelve months.

We prefer to breed bucks later than does where possible, from eight months of age. This is because their behaviour will change once they have fully matured due to the increase in testosterone which appears to occur at eight months. We have had males that at this age have become too dominant with their cage mates due to this increase in testosterone, and the decision has been made not to breed with them. Had we bred them earlier, we would have been unaware of this problem. This is a hereditary problem, and will often present in offspring when they reach maturity, hence the need for caution when breeding bucks.

There is no maximum age for a buck, he can breed until the end of his life! Fertility will decrease with age however, just as in humans.

Pre-pregnancy requirements

Our does must be a minimum of 250grams to breed a litter. Any smaller and the doe doesn’t have enough excess to safely raise a healthy litter without sacrificing too much of her body weight. The weight of the male isn’t really of consequence, but as for the doe, he must be healthy.

Pairing the lovebirds

We wait until we notice the doe is in heat, which is generally observed by the vibration/buzzing that is explained on the Behaviour Page. When the doe is in heat, we place her in with the buck. The buck will go over to the female and sniff her genitals to ascertain that she is female, and that she is in heat. The female will respond by buzzing and raising her rump. The buck will then mount the female and mate her. Mating is quick and frequent. Once mating has been witnessed, we will leave the doe with the buck for the night for the full length of her heat, which is usually 3-6 hours, and remove her in the morning. Bucks harass the does somewhat, which is why we don’t like to leave them in with them longer than necessary.

If this first one-night-stand doesn’t produce a litter, we will try again and this time keep the doe in with the buck until she is showing pregnant at which time the doe will be removed to her birthing cage, to prepare her nest unhindered by the attentions of the male. It should be noted that does come into heat immediately after birth. If the buck is still in with the doe at this time, she will fall pregnant again, and raising one litter whilst being pregnant with another is certainly not advisable for the does’ health.

Pregnancy behaviour

Photo of pregnant rat
Pregnancy hormines can bring about some interesting changes

Pregnancy will take a fair bit out of your doe. She will rest more than usual, and will become an eating machine. To help keep her energy up, and for the growing pinkies, offerings of protein such as boiled eggs, ham strips and dog/cat kibble can be offered. We offer this in addition to the normal diet of dried mix and one cooked meal per day as explained on the Nutrition Page.

As the pregnancy hormones kick in, your doe may undertake some rather startling behaviour changes! The hormones will cause your doe to become very protective of her cage and especially her nest area. If she feels you are invading her carefully prepared nesting space, she will nip you to tell you in no uncertain terms to back off. Once the babies are weaned and the hormones have stopped being produced, your does behaviour will return to normal again.

Pregnancy lasts twenty one days from conception. It is important to note, where possible, the suspected conception date so that you are aware of the due date and more importantly, if your doe has gone over the due date. Any more than a few days and she may be experiencing problems which require a vet visit.

Your doe will begin making a nest three to four days prior to the birth. Nesting materials should be provided for her to make her nest with. Be careful not to offer anything that has loose threads, such as cut up towel or cotton sheets, as the pinkies will get wrapped up in the threads which can cause loss of limbs and death. Polar fleece strips are the best material to use for nest bedding, it is washable and reusable, do not have threads, keep the pinkies warm and isn’t a heavy material. Once the pinkies are a few days old and the doe has settled into parenthood, we remove the fleece strips and wash them every three days to help keep the nest clean. Although you may have provided multiple nesting sites, does sometimes make their nest in the oddest of areas. To limit any risk of injury to the pinkies, make sure that the birthing cage does not have bars on the bottom that they can slip through or any other obvious dangers.


On the day of the birth, the doe will seem restless. You may find that she alternates between pacing up and down and lying flat out and may seem uncomfortable. Her breathing may be faster and more obvious. These are all signs that babies are on the way! The doe will birth in her nest, you will know the stork has delivered when high pitched squeaking sounds are heard coming from the nest. It is important to leave the doe well alone for at least twelve hours after the birth, longer if you do not know the doe well. This gives her the chance to recover from the birth unstressed, and give her new babies their important first few feeds.

Precious pinkies

Photo of fice pinky, baby rats on carpet
Rats are born blind, deaf and hairless

Rats are born, blind, deaf and hairless. They resemble jelly beans and are arguably quite odd looking at this stage of their life. They are entirely reliant on their mother to feed them, clean them and even help them go to the toilet. The doe stimulates them to defectate by licking their bottom, and will then eat any waste. This may seem an odd behaviour, but it is natures way of ensuring the nest area is kept clean of waste, which would hinder the health of the pinkies and the success of the litter.

If there are dark coloured bubs in the litter, their marking will start to become apparent as soon as twelve hours after birth and will continue to darken. Lighter colours, such as the ruby and pink eyed colours, will take much longer for markings to show. Fur will begin to come through around day eight, and by day ten the bubs will have a soft shiny fur pelt. Eyes will begin to open around day fourteen. Usually it will take a few days for all of the ratlets to open their eyes.


It is important that your litter is well socialised with humans and other rats before they are rehomed. Your pinkies should be handled daily, from two days of age. We have found that the least stressful way for the mother is to coax her out of her cage with one of her favourite treats, then to transfer her to another cage with a treat to distract her for a while. Mummy rats usually don’t nip in defence if they are not near their nest. During this time, clean any poo from the birthing cage, add food, change water and carefully remove the pinkies from the nest and hold them in your hand. Even though they can’t see or hear you, they will start to recognise your scent as non-threatening.

They will lose body heat very quickly as they do not have control of their temperature at that age, make sure to keep them warm whilst they are out of the nest. No more than five minutes is needed handling the pinkies at such a young age. Put them back into their nest before you put the Mum back in with them. The first thing she will usually when put back into the birthing cage is check her babies, and will panic if they are not in the nest.

When the pinkies are five days old, extend the holding sessions as they can now safely be away from mum for longer periods. If you handle your ratlets carefully every day, they will grow up to be very well socialised with humans.

When the ratlets are four to five weeks old, size dependent, we introduce them to an older, laid back buck that is tolerant. This helps with introductions to potential cage mates once they have gone to their new homes.


Female mother rat in a heap with all of her baby rats
Weaning begins between three and four weeks of age

Mum will start to wean her ratlets between three and four weeks of age, although they will still have the occasional comfort feed up to five weeks. By five weeks the bucks should be separated from their sisters and mother to ensure that there aren’t any unwanted pregnancies.

They are ready for rehoming between six and eight weeks of age. Litters vary in growth rate, due to the health of the mother, the number of ratlets in the litter and their genetic disposition. Some need a little longer before venturing out into the big wide world than others.