How Many Babies Do Rats Have? Monthly, Yearly, & More

by Morgan Mulac

How Many Babies Do Rats Have? Monthly, Yearly, & More


Improper breeding (commonly known as backyard breeding) is not something we condone, but we are aware that many of our audience members are either interested in becoming ethical rat breeders, or have taken in rescues that have been improperly sexed, so we want you to understand how to care for a pregnant rat and her pups properly.

No matter if you are a beginner to the profession of rat breeding or you've taken in a pregnant rat as a pet, it's important to know how many baby rats you're going to be expecting and what you can do to help the mom as much as possible.

In this article, we’re going to look over everything you need to know about rat litters, including a general look at their production, how many babies per litter you can expect, and the best way to care for a mom and her newborns.

Rat Reproduction: An Overview

In order to fully understand a rat's pregnancy and litter, we need to first understand the reproductive process of a rat. Most fancy rats reach sexual maturity around 6-12 weeks (more specifically, 6-10 in male rats, and 8-12 weeks in females.)

This is typically the time it is recommended to separate male and female rats to prevent unwanted breeding. But if you’re looking into starting ethical breeding or have improperly sexed rats, this 6-12 week period is the earliest rats can start breeding. Typically, experienced breeders will err on the side of caution and wait until the 12-16 week mark to start breeding.

Rats have a very short breeding cycle, lasting only 4-5 days before ovulation. All of this gives a very short window from sexual maturity to possible pregnancies.

When an unspayed female rat is in heat, she will typically vibrate her ears, arch her back when petted, and run in short and fast bursts.

What Happens During a Rat's Pregnancy?

The gestation period of a rat usually lasts 21-23 days. The symptoms and signs of pregnancy usually present throughout the duration of the pregnancy, but remain largely unnoticeable until the last week, when their appearance starts to change.

When a rat is pregnant, their behavior will begin to change as they prepare for their litter, this can look like hoarding food and increased nesting in their cage. Other behavioral changes include becoming territorial over their space, aggressiveness, and general personality changes.

Among the physical changes that may occur to your rat during pregnancy are weight gain (the biggest increase occurs immediately after conception and again just before delivery), an expanded abdomen, and enlarged nipples.

Although a female rat can breed 48 hours after giving birth, the ethical breeding strategy is to give a female rat at least two months before allowing her to get pregnant again.

How Many Babies Do Rats Have in a Litter?

While the exact number of baby rats in a single litter can vary due to many different factors, including the mother's age, health, and having a suitable food source, the average number of pups per litter is 6-12.

Another factor that can affect litter size is the type of rat. While rats like roof rats and Norway rats are not intended as pets, it’s interesting to look at how their average litter. Norway rats can have larger litters of up to 15-16 pups at a time, but the average is 8-10. Roof rats have significantly less, with the average being at 5-10 pups.

With regard to pet rats, providing the ideal environment for a pregnant rat and her offspring is vital. It is quite common for a mother rat to resort to eating the baby rats when she realizes there is not enough room or a lack of food to go around for all the rats. Despite its morbid appearance, this is usually done for the survival of any remaining rats.

Mother rat with baby rats

How Many Litters Can a Rat Have in a Year?

As mentioned earlier, rats can breed 48 hours after giving birth, doing the math, this means that a rat can theoretically have up to 17 litters a year. However, this number doesn’t include the time it takes to wean the baby rats or allow the mom to recover.

It is more realistic to expect about six litter per year from pet rats if you are practicing proper breeding procedures. Taking into account the average of 6-12 rats per litter, this means your rat could have up to 72 babies in a year!

Caring for Newborn Rats

As soon as your rat gives birth, you might be tempted to give her and her pups constant care and attention, but the best thing you can do in the first few days after the baby rats are born is to give them sufficient space and simply keep an eye on them.

If you notice any signs of complications from the pregnancy or the pups show any signs of illness, it is best to take them to a qualified exotic vet who can help.

Nesting Materials and Environment

As mentioned earlier, the proper environment is important for the health of the rat babies as well as the health of the mom. One of the most important aspects of the environment is the rat cage you keep them in.

Baby rats are much smaller, so your cage needs to have a deep bottom so they can't climb up to the bars and escape from it. However, a cage with bars is still important, since you need to make sure the rats have a sufficient amount of ventilation, which is why we don’t recommend tanks unless you have a cage add-on like this one.

Nesting is also an important aspect for a mom and her rat babies. Making sure you give the mom enough supplies to build a proper nest is key here, as she will know the best nesting setup for her litter. Proper materials for nesting included unprinted shredded paper, and brown paper bags.

Lastly, proper access to food is incredibly important, while the babies won’t be weaned for a few weeks, making sure that the mom knows that there’s plenty of food to go around will keep her calm and happy.

Weaning and Independence

At two weeks of age, rats begin to gain some independence, since their eyes open and they are able to start exploring their surroundings and eating bits of food in the cage. This period is also when you can begin to tell what types of pet rats you have, as their coloring and characteristics become more prominent.

In week three, you will be able to start socializing with the baby rats more as they become more active. There are some breeders or institutions that start weaning babies at this age, but weaning naturally can be beneficial to their behavior.

By week four, your rats should be drinking water and eating rat food, while still being supplemented by their mother's milk, this is the peak time to make sure the rats are properly socialized to humans.

It is recommended that rats should be separated by gender no longer than five weeks after they are born since this is the time when rats become fully mature and can begin breeding with each other.

Cuddling baby rats

Health Considerations for Breeding Rats

Breeding rats as a profession is a big undertaking, as there can be many health considerations potential breeders should be mindful of when deciding to breed a specific rat.

Like in humans, pregnancy can take a toll on a rat's body, and there can be complications from birth. It’s important if you’re choosing to breed rats to make sure they’re at the peak of their health, as well as in the right age gap for safe breeding.

If your rat has any illnesses or their body feels it will not safely carry to term, the rat is very likely to have a miscarriage and birth the babies prematurely, should this happen, it is advised to see a vet to ensure there are no complications.

Choosing the right age rat is important when breeding, as it can prevent age-related problems. The ideal range for rats to be bred is 4-5 months old at the earliest and should stop being bred at around 12 months of age to make sure they can live out their full lifespan without complications.

Breeding rats over the age of 8 months if they have never been pregnant before is not recommended, since their hips have grown in such a way that makes it difficult to give birth, which can be dangerous for the pregnant rat and potentially require a c-section from a veterinarian.

Signs of complications in the pregnancy and birth process include painful vocalizations (screaming is a common vocalization), prolonged labor, a pup stuck in the birth canal, and excessive bleeding. If any of these signs are noticed, it is crucial to get them to an emergency vet ASAP.

How Can Pet Owners Prepare for a Rat Family?

Before your rat's litter is born, it’s important to provide a safe, warm, and comfortable environment. This can be done by providing nesting materials, such as shredded paper towels or brown paper bags. To ensure the rats live in a clean and sanitary environment, nesting material should be changed regularly.

It’s also important to move the female rat to a cage of her own once you realize she is pregnant, as the behavioral changes can present as aggression toward their cage mates.

It is also important to monitor the mother and her babies for any signs of stress or illness. If any signs of stress or illness are present, it is important to seek veterinary care.

It is also important to socialize the rats with humans. Providing enrichment activities such as puzzles and toys can also encourage social behavior and prevent boredom.

Experience the Fascinating World of Rat Families

Owning a rat can be a rewarding experience, and having a baby rat can make it even more enjoyable. We do not recommend casually breeding rats without adhering to ethical practices, but many owners choose to take on ethical breeding as a profession or rescue a pregnant rat and care for the newborn pups.

If an owner decides to breed ethically or care for a pregnant rat, they can expect to have 6-12 rat babies and then must provide them with four weeks of care in their mother's cage once they are born. For more information on quality rat care, check out our other blogs.


How quickly do rats multiply?

Rats multiply at a rapid rate. They can have a litter of 6-12 babies every three weeks and can have multiple litters in a year.

How many babies do rats have at once?

Rats that carry a full-term pregnancy typically have 6-12 babies at once in a single litter.

How many babies do rats have a month?

As rats can reproduce 48 hours after giving birth, it is possible to have rats born every three weeks. However, most ethical breeders give two months in between breeding to allow the mother time to rest and recover.

How often do pet rats have babies?

There is no doubt that pet rats should be separated in order to prevent pregnancies, however, if this isn't done, they can have babies every three weeks.


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Author Bio: Morgan Mulac

Morgan Mulac has been working as a freelance writer for five years and has developed a passion for exotic pets. Dedicated to learning about exotic animals from all over the world, she seeks ways to share her knowledge with new owners about how to better care for their animals. If Morgan is not researching or writing about exotic pets, you can find her enjoying a cup of coffee and planning her next adventure.

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