Research overview: the protraction-retraction mechanism of felid claws

Cat claws are often called retractable, but they are more accurately protrusible: at rest they are held back by elastic ligaments, and muscles actively pull them forward into action. This overview explains the mechanism, in which the terminal toe bone pivots and the claw is deployed by tendons of the deep digital flexor, then springs back when the muscle relaxes. Keeping claws sheathed at rest protects their points and keeps them sharp for hunting and climbing. Researchers describe the arrangement through comparative dissection, imaging of the toe joints, and modelling of the ligamentous spring. Why it matters: this elegant default-sheathed design distinguishes most cats from dogs, preserves a critical weapon and tool, and underlies behaviours from stalking silently to seizing prey and scaling trees.