How to Tell if a Rat is Pregnant? Here’s an A to Z on Rat Pregnancy

how to tell if a rat is pregnant

Rats are the most underrated pets. It is not commonly said, but rats are one of the best kinds of pets you can get. Unfortunately, they don’t live for too long( the average lifespan of a rat is 18-36 months), and they are not as low maintenance as people think. 

One of the issues pet rat owners go through is an unexpected pregnancy. This is why it is important to have all the information needed from A to Z about rats and their pregnancy. You should be able to know how to differentiate the genders, when to separate the rats, how to tell if a rat is pregnant and how to take care of her babies.

Reproduction and Breeding Rats

If you have a pet rat or you are looking to breed one, you should know all about the reproduction cycle of rats: when do rats reach sexual maturity, how long is the rat gestation period, and when is the optimal sperm production in rats?

Sexual Maturity in Rats

When a rat or any organism reaches sexual maturity, it can now reproduce. It is important to know when your pet reaches sexual maturity, especially if you have both females and males because they should be housed separately if you are not looking to have baby rats.

  • Male rats mature sexually at an age of 6 to 10 weeks.
  • Female rats mature between 8 to 12 weeks.

Male rats produce a smaller amount of sperm at puberty and cannot fertilize females until 6 weeks after reaching puberty. When a rat is 10–14 weeks old, it is the optimal sperm production. 

Male rodents can reproduce anytime after sexual maturity, but females are only receptive during estrus (heat).

Rat Gestation Period 

The average gestation time (the period where the fetus is developing inside the uterus of the female) is 21 to 23 days.

Factors That Decrease Reproduction

Just like humans and other animals, there are a lot of factors that can cause a failed pregnancy, such as:

  • Age
  • Malnutrition
  • Cold weather
  • Uncomfortable environment
  • Reproductive system diseases
  • Dehydration 

How to Tell if a Rat Is Pregnant

Pregnancy can be hard to detect in rats and can be spotted only until the last week. Your pet rat will go through behavioral changes and physical changes, but these can be detected most of the time only after 2 weeks of pregnancy. Sometimes you won’t even detect any changes, and you get surprised by a litter of rats.

1. Behavioral Changes

Just like humans, when rats are pregnant, it alters their hormonal balance. Usually, your friendly female rat will become more aggressive and territorial and will have lots of mood changes. Your rat might bite you if you make her feel uncomfortable. 

BUT some people have noticed that rats who are already aggressive before pregnancy can become friendlier when they are pregnant. 

Female rats will accept to mate with a male when they are in heat. But when the rat gets pregnant, she will refuse the male, and this act will help you determine that your rat is carrying babies. 

You need to take care of your pet rat more than ever during this period. 

2. Nest Building 

A few days before a pregnant rat gives birth, Hormonal changes won’t only affect her mood but will also trigger her natural instinct to nest. When the female starts building her nest, you should prepare yourself to have newborn rats anytime soon. 

Usually, they will build their nest out of shredded paper, pieces of clothes, or any small comfortable shreds that can make a simple and cozy nest. When building it, female rats will make sure to make a space for their newborns to hide.

How Can You Help : Provide the mom with a cage that’s easy to access, place it in a safe, calm area, and add comfortable materials like newspaper or tissue paper so she can use it to build a nest. 

3. Appetite Change 

Another change that happens during pregnancy is appetite change. You will notice that your pet is eating more than usual and always demanding food. This is normal for a pregnant rat who is trying to get all the nutrients needed. 

Be careful; malnutrition and lack of water can lead to abortion or mutated newborns. You should observe your pet’s bowl often to spot the increased appetite. 

4. Visible Teats 

The nipples of a nonpregnant female rat are usually not visible. You need to palpate her belly to feel them. But during pregnancy, they get more and more visible and will stay until she is done breastfeeding. 

The nipples usually start showing after 2 weeks of pregnancy (one week before giving birth).

Why Do Nipples Show When the Rat is Pregnant : When the rat is pregnant, she will lose fur around her breasts. This process will help her newborns find her nipples easily. 

Be careful when you feel that your rat’s nipples are showing. Do not examine her belly by yourself because the fetuses are extremely fragile, and you might harm them. Instead, you can ask your vet for help, and they will determine if she is pregnant or not.

5. Mucous Plug

When your rats mate, you may notice plugs appearing on her vagina, this means that the mating was successful. These plugs are formed by mucus and secretions of a male rat’s glands. They are secreted after mating. 

The job of this mucus is to create a barrier that holds the sperm in the female’s vagina and prevents other males from impregnating her.

6. Weight Gain

The average weight of a female ranges between 250g and 300g. When your rat is pregnant, she will for sure gain weight. But weight gaining is not a very specific sign that can determine pregnancy. On the other hand, if she is showing some or all of the signs listed above as well as gaining weight, this means your rat is probably pregnant. 

Usually, pregnant rats gain 71g while pregnant, which is almost equivalent to 40% of their normal body weight. 

There are other factors that might cause weight gain, such as overeating. It is better to always monitor your rat’s food and weight. If your rat is losing too much weight without explanation, it is important to immediately call your vet.  

How to Take Care of a Pregnant Pet Rat?

When your rat is pregnant, she will need extra care and love. You should be able to provide her with what she needs so she can give birth without any complications.

You can follow the following steps:

  • Provide high-protein food and give her as much as she wants.
  • Provide clean and fresh water at all times.
  • Provide a clean, comfortable cage she can use as a nest with some tissue, clothes, or newspapers. The cage must be safe and easy to access.
  • Separate her from other rats.
  • Provide a calm environment away from any danger or disturbance.
  • Always monitor her progress and keep an eye on any unusual behavior.

Related Article: Neutering Rats

How to Take Care of Baby Pet Rats? 

Now that your rat has given birth, it’s time to take care of her newborns as well. The baby rats are tiny, about one-and-a-half-inch long, blind, deaf, and heartless. There’s not a lot of work to do since the mom will be taking care of them for the first 3-4 weeks and lactating them. 

But there are some points you need to know that will make it easier for you to take care of them:

  • Separate the males from the females when they are 4-5 weeks old to prevent unwanted pregnancy.
  • The nest has to be comfortable and safe. Try to provide heating so your baby rats can stay as warm as possible.
  • When they are first born, baby rats get all their nutrition from their mother’s milk. 
  • Provide the mother with good quality pellet food formulated for rats and add some vitamins. It is necessary for the mother to be healthy so she can lactate her newborns.
  • When the baby rats start eating, feed them good quality food supplemented with nuts, vegetables, or cereals.
  • Stay away from toxic food for rats
  • Rats get easily bored, so you should socialize with them and get your pet rat as a companion. It is preferable that it’s from the same gender to prevent unwanted pregnancy.
  • Sexing your baby rats is important so you can know who to separate. Starting 2 weeks old, it becomes easier to find out the gender of your rat. Usually, males have visible scrotums that can help you differentiate them from females.


It might be tricky to know how to tell if a rat is pregnant. There are many signs that can help you figure it out, like behavioral changes, nest building, appetite change, visible teats, mucous plugs, and weight gain. 

If you are trying to avoid pregnancy, make sure to know how to know what gender your rats are and to separate them. If you are looking to breed rats, you must know how to take good care of a pregnant rat and her kids. 


  1. Signs Your Pet Rat Is Pregnant
  2. How Can You Tell A Rat’s Gender?
  3. Breeding and Reproduction of Rats
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