How does a cat sharpen its claws?

Human fingernails and cat claws are made from keratin and keep growing their whole life.

Human fingernails do not retract (go in and out) – they do not go back into the skin to make them invisible. 

Most cats and wild cats have claws that are exposed or protracted when they use them and are hidden, sheathed, or retracted when they don’t need them. 

The cheetah does not have fully retractable claws – its claws are classified as semi-retractable but are always exposed (seen).

To catch and kill their prey, cats need sharp claws. To climb trees, cats need sharp claws. 

The fingernail of a human (and a dog) grows slowly lengthwise out of the skin. 

However, the fingernail (claw) of a cat grows layer by layer with a protective transparent (see-through) sheath that grows over the claws. A sharp inner claw is growing at the same time. 

When the outer layer of the cat’s claw becomes blunt or loose, it is removed so that the next layer—the next sharp claw—can become the outer layer. 

The cat knows that the blunt sheath has to be removed because it is uncomfortable, so it scratches on a piece of wood to remove the sheath and allow the inner claw to show. The new claw also has a protective sheath, and the process continues. 

The cat also has a good stretch when it scratches a piece of wood, so that it can stretch its muscles, especially its strong shoulder muscles.

Really, the cat is not sharpening its claws. It is removing the outer layers of its claws to let the sharp inner layers come to the surface, ready for more catching, killing, defending, and climbing.  

Photographer: Martina Nicolls

Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM