Do Guinea Pigs Have Periods?

Guinea pigs are mammals and as such females have a uterus so you are wondering if they have periods like humans, dogs and others? You might have seen some bloodstains and mistakenly assumed that these are related to your guinea pigs’ periods.

Guinea pigs don’t have periods nor bleeding as humans do. However, they have estrus cycles. They will be in heat every two or three weeks ( 14-20 days) and will be receptive to males for 8-11 hours ( usually during nighttime).

Young females reach their sexual maturity when they are 2-3 months old but shouldn’t mate before they are at least 4-5 months old and weigh about 1-1.5 pounds. The first pregnancy shouldn’t happen after the female turns 7 months due to possible health complications.

How Often Does My Female Guinea Pig Go In Season ( Heat )?

They have heat cycles that last for 14-20 days in which they are fertile and ready to mate in a period of 8-11 hours. These cycles repeat constantly throughout the year.

Female guinea pigs are sexually mature from an early age – 2-3 months old but shouldn’t mate that young. They can produce litters until they are 5 years old.

The interesting fact is that guinea pigs can go into heat right after delivery and this is called postpartum estrus. She can mate again around 15 hours after delivery which means that she can be pregnant again and still nursing the existing litter. So be careful, never place a pregnant or nursing female close to a male guinea pig, to avoid any unwanted litter.

How To Know If My Female Guinea Pig is In Heat?

If you catch your piggy chasing her cage mates more than usual that could mean that your sow is in heat. Even if she doesn’t have a habit to chase her friends at all, once in heat, she will most probably do that.

Another sign is also a form of dominant behavior. She could do climbing/ mounting on her cage mates.

If you come closer, you will able to notice a swollen vulva and that would be the clear sign that your piggy girl is in heat.

Some owners have reported other signs as well. One of them is popcorn shaking. Maybe your piggy normally performs that but these days it’s more often.

What else is possible is purring/rumbling noise, again more frequent than usual. The sow in heat might be more aggressive towards her cage mates as well.

If you haven’t had too much experience with guinea pigs so far, maybe at first you miss the signs that one of your sows is in the heat but if you make a mistake and let a boar to be in her vicinity, believe me, he won’t miss them.

When The First Pregnancy of A Guinea Pig Should Occur?

Although female guinea pigs are sexually mature very early, at the age of 2 months, they shouldn’t mate before they reach a certain weight and get a little bit older ( 4-5 months of age )

If you want to breed your female guinea pig you should know a few things. First of all, breeding is not recommended unless you want to provide quality care for babies or to find a proper home for each one of them.

Remember that guinea pigs rescue centers are full of unwanted guinea pigs so please don’t produce more piggies unless you really want to take good care of them.

Another issue is the pregnancy itself. Pregnancy in guinea pigs poses a high risk. I don’t know if you knew but almost 20-25% of guinea pig mums die during or after the delivery, due to numerous complications. Stillborn and miscarriages are pretty common as well.

The most important guinea pig breeding consideration is the age of the female that mates for the first time. That should happen before she turns 7 months of age. Why?

The pregnant sow experience a very enlarged belly especially in her later stadium of pregnancy ( it’s not uncommon to double their body weight).

In order to deliver babies safely, the separation of the pelvis develops right before she will give birth (it reaches up to 1 inch just before the delivery).

That is a good sign as you won’t be able to determine the potential day of delivery due to the very long gestation period ( 57-65 days) and the fact that sows don’t make nests.

If your sow is going to deliver her first litter after the age of 7 months the separation of pelvis won’t develop, creating a very hard and potentially tragic situation.

If this happens your sow won’t be able to deliver her baby naturally. The cesarean section must be performed, otherwise, her life and the babies’ lives are in danger.

Why Is My Female Guinea Pig Bleeding From Her Bottom?

The important thing you should know that sows don’t make any mess neither leave any discharge including blood during their estrus cycle.

So if you notice that your sow is bleeding from behind, you should visit your vet for further consultation as your piggy can have some of the following health conditions that requires vet’s attention :

Urinary tract infection or UTI as well as cystitis ( bladder inflammation) can cause the presence of blood in the urine. You can make a mistake thinking that the blood comes from the uterus but in reality, the blood appears in the urine as a result of UTI or bladder inflammation.

Not every pink/red urine is a sign of blood presence. If you would like to know more about this topic do read our article ”What color should a guinea pig urine be?”

If you notice that your guinea pig pees more than usual, experience pain while urinating ( makes painful squeaking sounds) then you should take your piggy to the vet who will run some tests and easily determine what the treatment should be.

I have also read good advice – if you notice a pee of your piggy you can collect it with a syringe or pipette and take it to the vet for analysis.

Pyometra is a very serious health condition that can be fatal if left untreated. Pyometra is the infected womb. The most usual signs of this disease are

  • weakness
  • lack of appetite
  • vomiting
  • discharge from the vagina ( pus)
  • drinking water more usual

Pyometra is such a strong infection that regular antibiotics won’t help. Instead of that, the surgery is necessary. This surgery will also involve spaying your piggy. In fact, if your piggy is spayed, the chances to catch pyometra are very slim.

Uroliths or bladder stones are pretty common in guinea pigs. Piggies ingest too many minerals through the food and water, which turn into tiny crystals which further form stones in the bladder and cause bleeding in your cavy.

The main sign is difficulty and pain while urinating. The surgery is the only way to help your cavy. The vet will surgically remove the bigger stones.

Although guinea pigs are prone to this problem, you shouldn’t give your piggy the food rich calcium too often ( kale, spinach, Swiss chard, broccoli).

Also, make sure you offer the freshwater to your cavy every day. Avoid tap water if you don’t drink it, it’s not good for your pet too.

Tumors less common but still can happen and almost always cause bleeding. The cancerous growth can be located in the urinary tract or elsewhere in the body but this blood that comes out easily can be mistaken for menstrual bleeding.

Depends on the type of tumor, the vet will decide whether he will perform the surgery or not. Sometimes benign tumors can be kept under control with medications.

Bottom line- you cannot be sure that the bleeding you have seen is a sign of a tumor. However, the visit to the vet is a must, and if he suspects something like this he will perform MRI or ultrasound to determine what’s wrong with your cavy.

At What Age Do Female Guinea Pigs Stop Being Fertile?

Although it’s said that guinea pig females are fertile up to 4 or 5 years of age, the perfect breeding life should end after the female is 2 years old. Every pregnancy after the period is highly risky and can be fatal.

With aging, the litter size decreases but the possibility for complications increases.


Guinea pigs do have estrus cycles but these are not like menstrual cycles in humans and are not followed by bleeding or any other type of vaginal discharge.

Sows come in heat every 2-3 weeks throughout the whole year. They are receptive to males for half of the day (most probably during nighttime). You will notice that piggy in heat is more aggressive and prone to dominant behavior towards her cage mates.

If you notice any bleeding from her rear end, you should consult a vet as she can suffer from infection or tumor. Whatever is the reason, she needs the vet’s help.

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