July 16/2025

                             

What Is a Cat’s Primordial Pouch?

By Janelle Leeson. Reviewed by Barri J. Morrison, DVM

3/21/ 2024

Does your cat have a belly that sways side to side? That’s not fat, says Dr. Nicole Savageau, a veterinarian at the mobile veterinary service The Vets. It’s their primordial pouch—loose skin near the rear legs that feels floppy.

Here’s what to know about a cat’s primordial pouch, including why cats have them.

What Is a Primordial Pouch?

When your cat is standing, take a look at them from the side. Do you notice a loose belly that hangs down a little? It may look like an overweight cat that recently lost a lot of weight but retained the extra skin. Rest assured, this extra skin has more to do with genetics than your cat’s body condition.

This is a cat’s primordial pouch, a loose flap of skin on a cat’s underside that hangs between their rear legs. Cats are the only animals that have a primordial pouch (including wild ones like lions & tigers!), but some cats have a more pronounced primordial pouch than others. 

Why Do Cats Have a Primordial Pouch?

Experts aren't 100% sure about the purpose of the primordial pouch, but they have some theories:

Protection: A primordial pouch might shield a cat’s vital organs during fights or rough activities.

Flexibility: It allows the abdomen to stretch during movement, making cats even more agile. 

Food storage: It could help accommodate larger meals when a cat eats a lot at once.

Heat regulation: It might aid in temperature control by allowing air circulation.

According to Savageau, the feline primordial pouch might not have a function at all these days. “It could be an evolutionary relic trait left over from wild ancestors,” she says.

When Do Cats Develop a Primordial Pouch?

You won't spot a kitten with a big, floppy primordial pouch. “It develops over time as the cat matures,” Savageau says. The pouch usually becomes more pronounced as cats reach adulthood, usually around 6 months to 1 year old. But it's not obvious in all cats & can vary in size. 

Why Is My Cat’s Primordial Pouch So Big?

No matter how big or small your cat’s swaying belly flap is, Savageau says that having a primordial pouch isn’t an indication of your cat’s overall health or whether they're overweight or underweight. “There can be variations in the size of the primordial pouch among cats, with genetics playing a role,” she says. 

According to The International Cat Association (TICA) breed standards, the Thai cat breed typically has a smaller primordial pouch than most other cats, with a mostly level underbelly & only a slight amount of loose skin. Meanwhile, the Pixiebob breed is likely to have a large primordial pouch. 

Just like in humans, a cat's skin tends to sag, stretch, & lose elasticity with age. So don't be alarmed if your kitty's belly seems to sway a little more as they become a senior cat.

Feline Primordial Pouch vs. Body Fat 

If you’re still unsure if it’s your cat’s primordial pouch you’re looking at or fat, Savageau has some tips for differentiating the 2:

 

                                 Primordial Pouch                                                       Fat

Location                On the underside between the rear legs            Distributed around the body

Feel                        Loose & floppy                                                Firm or squishy

Body shape           Balanced body, defined waistline,                    Round in appearance, lack of

                              floppy underside                                               defined waistline

 

Focus less on the size of your cat’s belly flap & more on their body condition score (BCS), a visual tool veterinarians use to determine if cats are at their ideal weight.

You can do this by looking down at your cat from above. A healthy cat will have a noticeable waistline while overweight cats will not. 

Then, gently run your fingers across their ribs. A cat at an ideal weight should feel similar to your knuckles being rubbed on an open palm. If your cat is overweight, there will be a layer of fat covering their ribs. An underweight cat’s ribs may feel prominent, similar to the back of your knuckles when making a fist. Your veterinarian can demonstrate this assessment at your next visit. 

Helping your cat lose weight won't make your cat’s primordial pouch smaller, but "maintaining a healthy weight through a balanced diet & regular exercise can help prevent excess fat accumulation," says Savageau.

If you’re unsure whether your cat is at a healthy weight or would like tips to help them reach their ideal weight, work with your vet.

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