Domestic cats (and all wild cats bar the cheetah) are known for their retractable claws. All the experts say it online but I disagree with them. To describe the claws as retractile or retractable misleads the way the tendons and muscles work.
The default position or position of rest for a domestic cat’s claws is retracted, which lifts them off the ground to a large extent.
The cat has to make a positive decision to extend the claws so that they become visible and start fully functioning. In a strict sense this means the claws are protrusible or protractile not retractile or retractable.
The difference between protractile and retractile is important in this instance. If the claws were retractable the cat would have to take positive steps and use his muscles to retract his claws for hours on end. This would be impractical and a waste of energy as the claws are normal tucked away. They are used for emergencies, stretching and when scratching, for instance.
Because the claws are retracted when at rest they maintain their sharpness like a sword in a scabbard. Cat owners know this when scratched. It seems to me that in the rest position the muscle pulls on the tendon which retracts the claw. No effort is needed.
The claws of indoor/outdoor cats are usually less sharp on the forepaws because they are used often and come into contact with the ground and other objects frequently. As a result they become slightly blunted or simply slightly less sharp. Indoor cats rest more which means there is less opportunity for the forepaws in particular to be blunted by day-to-day use.
It is worse for elderly cats. Their claws can grow too long and into their paw pads causing harm and pain. Cat guardians need to inspect the paw pads of elderly cats regularly and trim them when necessary.
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