Cats can have a primordial pouch. Image Credit: Christine Koh/iStock/GettyImages

You watch as your cat walks away, and you see this belly flap swinging from side to side. While it might be natural to immediately jump to the conclusion that you need to get your cat on an exercise routine, it's actually a normal part of the anatomy. That's the cat's primordial pouch, also known as a belly flap or abdominal flap. This pouch, present in cats of both genders and more obvious in some breeds than in others, has a purpose.

What is the primordial pouch?

Just about every cat has a flap of skin that dangles back and forth as he walks. Carolina Tails explains that the reason behind the primordial pouch used to be that it was caused by skin becoming stretched out as a cat gained weight. Now, experts know that's not the case, even though there is no consensus on the actual reason for the primordial pouch.

Sometimes, this extra jangly flap of skin has the nickname "spay sway." Carolina Tails says experts all agree that the primordial pouch has nothing to do with being spayed or neutered.

Purpose of the primordial pouch

Explanations for the primordial pouch are that it protects vital organs during cat fights, or it allows cats to be more flexible when running and jumping, or that the primordial pouch gives cats room to store some extra food when they overeat. Woman's World explains that when a cat is hunting, she may stretch out to her fullest body length, and the cat pouch may give her more room to stretch. If a cat gets clawed in the stomach during a fight, it's possible that the injury may affect just the pouch and not the cat's internal organs.

It's also possible that this cat pouch is an evolutionary holdover that gives cats a place to store fat just in case they don't know where their next meal is coming from. Other animals have similar anatomical fatty areas, such as female rabbits, who store fat under their chin.

SepiCat says the primordial pouch is more obvious in some cat breeds than others. It is said to be most obvious in purebred cats, including the Egyptian mau, Japanese bobtail, pixie bob, and Bengal cat. This cat pouch may also be more common in male cats than in female cats.

Is my cat fat?

You might think that the fatty flap of skin means your cat needs to lose weight. Having a cat pouch doesn't necessarily mean your cat is obese. While the primordial pouch is in the belly area, when you observe your cat walking, you will notice that the flap is actually more toward the rear.

Carolina Tails says you can check for a fat cat by running your hands down your cat's sides. If you can feel his ribs and they are not protruding, then your cat is in good shape. An overweight cat will have a round belly, and you won't be able to feel his ribs by just gently touching his sides.