The African lion has a remarkable adaptation for hunting. Unlike other carnivores that commonly have permanently extended claws, lions (and most other cats) sport protractile claws. With this protraction mechanism, the claws are either passively retracted within the paw or actively extended out of the paw. In the paw’s relaxed state, elastic ligaments and tendons hold the claws within sheaths of skin. In this state, the claws are protected from the wear and tear that comes from walking on rough ground. Using this covering is like keeping a sword in its scabbard to protect it from becoming dull. When the lion is ready for action, it uses muscles to actively straighten its toes and extend its blade-like claws from their sheaths. This specialized arrangement enables the lion to control when to use its sharp claws for hunting, as well as climbing and mating.
This summary was contributed by Sam Gochman.
“Cats can grip with their front paws with more than just flexibility: they have protractile claws, like blades that simultaneously fire from each paw! (To call them ‘retractile’ is to misunderstand the animal’s behavior.) In a normal relaxed state the claw is sheathed, but when the paw is extended, ready to strike (in a similar move to our opening our hands wide) the curved claws project.” (Tabor 2003: 14)
“The bones at the end of each toe are usually pulled up and back by strong elastic tendons, withdrawing a lion’s claws into sheaths of skin. This arrangement keeps the claws from becoming blunted by contact with the ground as the lion walks or runs. When it needs them for seizing prey, the lion contracts muscles that straighten the toe bones and make the sharp claws protrude from their sheaths.” (Marshall Cavendish Corporation 2010: 171)
“Cats are renowned for their protractile claws. Both the terminal and penultimate phalanges of felids… are modified to allow passive retraction and active protraction… The claws remain hidden within fleshy sheaths, being held in place by ligaments and tendons, so that they are not blunted by contact with the substrate.” (Kitchener et al. 2010: 93)