The reasons why domestic cats curl up in a ball when sleeping

Often domestic cats curl up in a ball when sleeping or snoozing. It is a very typical domestic cat behaviour with which we are very familiar. Why do they do this? They don’t always do it. Whether they do or not depends on the ambient (environmental) temperature. If it is a little chilly, they’ll curl up. If it is warm or hot, they might spread out and even present their belly to the world if the place is very safe.

Two useful tags. Click either to see the articles: Toxic to cats | Dangers to cats

Here are the reasons why domestic cats curl up in a ball when sleeping. The overall reason is heat retention and safety.

Heat retention: when a cat is curled up in a ball shape their surface area to volume ratio (S/V) becomes smaller and more effective in retaining body heat. Bigger animals are better able to retain body heat than smaller animals which is why, in the cat world, the Siberian tiger is much larger than the Sumatran tiger. Siberia is cold while Sumatra is warm. The science of the S/V ratio is quite technical. My artificial intelligence computer friend describes it thus:

“Large bodies, such as objects or organisms, tend to have a lower surface-to-volume ratio compared to smaller bodies. This is primarily due to how surface area and volume scale with size. Surface area refers to the total area of the outer surface of an object, while volume refers to the amount of space occupied by the object. When an object grows larger, its volume increases at a faster rate than its surface area. This is because volume is a three-dimensional measure, scaling with the cube of the linear dimension (length, width, or height), while surface area is a two-dimensional measure, scaling with the square of the linear dimension. In summary, the lower surface-to-volume ratio in larger bodies is a consequence of the different scaling rates of surface area and volume with size.”

Poe – an AI computer. Like I said it is a little technical 🙂

In other words, there is less heat loss through the cat’s skin when they curl up. The opposite occurs when they spread out. They lose body heat which may be applicable if it is hot, subject to safety concerns.

Another aspect of heat retention and a linked process is that one surface of the cat’s body comes into contact with another when they are curled up. These surfaces emit heat into each other and therefore into their body. There is little heat lost to the atmosphere.

Safety: when domestic cat is curled up, if they are a tabby cat (and the tabby coat is the original coat), they look like a snake (see below). This is a defensive measure to help protect them at a vulnerable time. The cat has evolved to learn this trick in the same way they learned to copy the snake’s hiss to scare away predators and hostile animals. They copied that from the snake too. The snake is universally understood among the animals to signal danger.

Also, another one of the reasons why domestic cats curl up in a ball when sleeping is to help protect their vital organs.

And thirdly it feels comfortable partly or mainly because of the above factors.

These are all instinctive behaviors inherited from the domestic cats wildcat ancestor. The image below shows the similarity between the coiled snake and curled up ocelot, one of the small wild cat species.

Curled Cat Coiled Snake Comparison
Curled Cat Coiled Snake Comparison. Image: PoC.

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