What Guinea Pig Breed Is the Largest? | All You Need to Know

When I first adopted my guinea pigs, they were very young. I loved feeding them, cuddling with them, and watching them grow. They are now full-grown at four years old. My oldest is the largest one, and she measures about 10 inches long. In comparison to her sisters, she looks huge, so imagine my surprise when I found out that some guinea pig breeds can grow even larger.

So, what guinea pig breed is the largest? The Rex, a purebred guinea pig breed from England, is the largest breed in the species. They can grow up to a foot and a half long, to which they grow full-size by the time they are two years old. Rex guinea pigs require little maintenance, and they are one of the most affectionate breeds.

Some Rexes develop into lap pigs, meaning that they love to sit in your lap as you show them affection. They don’t require any special diet, in comparison to other breeds. Caring for them requires minimal effort. They make perfect first pets for your children, but you may discover that you’ll form your own bond with this sweet creature. Read on to learn more.

The History of the Rex Guinea Pig

In South America, wild guinea pigs were great food sources. From 1200 to the first half of the 1500s, the people of South America domesticated the Rex guinea pig for food. They also served a religious purpose, for Mesoamericans used guinea pigs as sacrifices to their gods.

What Does a Rex Guinea Pig Look Like?

What Does a Rex Guinea Pig Look Like

As the largest species, the Rex can grow to about 18 inches long. They are a short-hair breed with fur that grows to only a centimeter long. This dense, straight fur is easy to maintain with regular grooming.

No two Rex guinea pigs look alike because the process of domestication resulted in a multitude of colors and patterns in their coat. For the most part, Rex guinea pigs have black, brown, and red fur. They have sharp incisors that they wear down by chewing on roughage and other fruits, vegetables, and food.

Rex guinea pigs have longer petal-shaped ears than other breeds, and they have big eyes on each side of their face. Their nails can grow relatively quickly, so they need weekly trimmings. If their nails grow too long, they can cut into their feet or cause injury during their grooming rituals.

What Does Rex Guinea Pig Eat?

Guinea pigs need a special diet to meet their nutritional needs. There isn’t anything special in Rex’s makeup that changes their dietary needs compared to other breeds. All guinea pigs need a freshwater source, pellet food found in any pet store, and hay. Either Timothy Hay or Alfalfa Hay is perfectly fine; the type of hay that your guinea pig will eat depends on their taste.

A selection of fruits and vegetables gives your pet the vital nutrients it needs to stay healthy. All guinea pigs cannot produce vitamin C on their own, so they need to eat sources of this vitamin daily. Almost all of the fruits and vegetables that guinea pigs like to eat have vitamin C in them, giving them a healthy source of nutrients.

How to Care for a Rex Guinea Pig?

How to Care for a Rex Guinea Pig

Rex guinea pigs are a favorite among first-time owners because caring for them is very simple. They make great pets for children who understand that they need to treat their guinea pigs gently. The care that Rexes require doesn’t vary from other breeds.


Rex guinea pigs have short, thick, and coarse hair that is easy to maintain with regular brushing. Their nails need to be monitored because they grow quite long relatively quickly. You should use clippers designed for animal nails, which can be found in any pet store or online shop. The clippers resemble scissors, with a rounded edge that cuts the nails.

Keep an eye out for their nail bed, which has a faint pink coloration on the part of the nail closest to the foot. If you accidentally cut into the nail bed, your guinea pig will start bleeding and may yelp in pain. Guinea pigs need bathing only three or four times a year since they groom themselves. If their fur gets dirty, it’s safe to bathe them more than the recommended amount.


A guinea pig’s natural diet includes water, food pellets, and hay. You can feed your pet natural food sources, such as fruit and vegetables, for their daily nutrition. Most guinea pigs love fruit, but these can be high in sugar. It is better to feed them vegetables more often. Some of these foods, such as broccoli and cauliflower, can upset your guinea pig’s stomach if you feed them too much of it.


Guinea pigs are highly social creatures, and they thrive with other guinea pigs in their cage. It is best to adopt two Rex pets at the same time so that they can grow up with each other. If you are unsure if you want to adopt more than one, keep in mind that your new pet will require extra love and attention from you.

If you introduce another guinea pig into your Rex’s habitat, monitor their interactions to make sure that they will get along. Although Rex’s are very friendly and social, they may not like the new cage mate. Also, although it is less common, some guinea pigs may not bond. If your pets do not share space well, you can place them each in individual cages next to each other so that they can still socialize.


A guinea pig cage should have enough space for all of your guinea pigs to move around, burrow, play, and eat comfortably. On average, a 30” x 36” cage is large enough for one guinea pig. If you have more than one, you should buy a cage that measures 7.5 feet squared for each cage mate. Rabbit cages are a good alternative for housing more than one guinea pig, as long as it meets the size requirements.

When cleaning your Rex’s cage, take them out and place them in a playpen or a small, open container with a blanket or other soft surface so they can play. Use gloves or a scooper when handling dirty bedding. You should clean your guinea pig cage using gloves or a scooper, replacing the bedding around once a week. You may need to do this more often if you have more than one guinea pig.

Once a week, after you remove the bedding, clean the surface with an animal-safe cleanser. Dawn works exceptionally well, but there are specific cleansers made for guinea pig cages. For their bedding, paper shavings are best because they do not harm your guinea pig’s feet or stomach when they walk around.

How Long Should You Spend With a Guinea Pig?

How Long Should You Spend With a Guinea Pig

Guinea pigs love attention, and the Rex is one of the friendliest breeds. Although each guinea pig has its preference for how much attention it likes, spend as much time with your pet as you can. If they get nervous or fidgety, this means that they are anxious and they want to go back into their home.

When taking your guinea pig out of the cage, make sure that you hold them correctly. Place one hand under the belly and one under the backside to help them feel secure. Since Rexes are larger than other breeds, this is always a two-hand job. Guinea pigs love cuddles, so place them in your lap or on your chest when showing them attention.

Although Rex guinea pigs are rarely aggressive, they will show you when they are unhappy. If they bite or bare their teeth, they are scared, or they feel threatened. Place your pet back in the cage if they show this behavior.

Related Questions:

How Do I Know My Rex Guinea Pig Likes Me?

Understand how your guinea pigs show their emotions. As they bond with their owners, guinea pigs show signs of affection and satisfaction during handling. They will make soft, squeaking sounds when they are happy, and they love to chatter.

Whistling is common when they are extremely happy, usually around mealtime. If your Rex is unhappy, he will make short, loud chirps to let you know that they feel uncomfortable. If your pet starts throwing its head back, fidgeting, or hissing with bared teeth, this means that your guinea pig is angry and aggressive.

How Do I Know if My Rex Guinea Pig Is Sick?

Like all pets, guinea pigs get sick from time to time. If you notice changes in normal behavior, such as decreased appetite or lethargy, make an appointment with your local exotic animal veterinarian for a check-up.

Changes in their waste, such as diarrhea or bloody urine, are a significant cause for concern. If you notice that your guinea pig has crust around its eyes, or the eyes are runny and receded, this may indicate a serious health issue.

List of Sources

Caring for Your Pet Guinea Pig

A Care Guide for Your Guinea Pig (Cavia Porcellus)

Guinea Pigs