When someone talks about a natural predator, most people think of cats. It could be any type of cat, from a lion, tiger or leopard to a cheetah, lynx or even a house cat. Known as one of the most purpose fit body designs they are sleek, powerful yet stealthy, strong yet lithe. There is definitely a lot to admire about their form. One of the most basic things we learn about felines is that they are able to retract their claws at will. Cats claws have fleshy sheathes that they can retract the claw into to protect the sharpness and keep them in tip top condition. This is a bit of semantics but when relaxed, a cats claws are drawn in and sheathed. So technically, cats extend their claws.
As you can see in the picture above, the digital flexor tendon is connected to bone of the claw. The digital flexor tendon is also connected to a muscle on the other side, as the muscle contracts, it pulls on the distal phalanx which then rotates around the pivot point, extending the claw out of the fleshy sheath.
Photo by Sammy Wong
The other interesting thing about cats claws is that they are not all made equally. While all cats share this anatomy in their claws, some cats claws are unable to be sheathed. The cheetah, the worlds fastest land mammal is unable to sheath its claws. This is because of the cheetahs lifestyle. The cheetah is the worlds fastest mammal, and when its running, it needs as much grip as it can get while changing direction on a dime. The tail helps with balance but unless the cheetah has grip, its not going anywhere, that's where the claws come in. The claws are naturally unsheathed so that they can help the foot grip the soil better.