London's Royal Mews takes its name from the moulting of royal hawks
In medieval English, moulting was called mewing, from the French muer. The King's hawks were kept in the Mews while they shed their feathers, and after Tudor times the building became stables, carrying the old word with it. Shedding skin, fur, feathers or a whole exoskeleton is how countless animals renew themselves.
Moulting, also called shedding, sloughing or, in many invertebrates, ecdysis, means casting off part of the body for some benefit, at a set season or stage of life. What goes can be skin, hair, feathers, wool, or in arthropods the entire outer skeleton, sometimes including insect wings.
Feathers are dead once grown and wear out, so adult birds replace them at least once a year, often more. They do it gradually and usually symmetrically, old feathers dropping as pin feathers push through, because a bird must keep enough plumage to stay warm and dry. Feathers make up 4 to 12 percent of body weight, so regrowing them is costly, and moults tend to follow breeding while food is still plentiful. Some species lose all flight feathers at once and must hide in safe, food-rich places until they regrow. Genuine bald patches usually signal illness or parasites rather than moult. A 2023 fossil study concluded that moulting probably evolved late in the bird lineage. In the United States more than 75 percent of commercial egg-laying flocks were force-moulted in 2003, usually by withholding food for one to two weeks, which cuts body weight by a quarter to a third and restarts laying.
Snakes rub their heads against rock or wood until the stretched skin splits, then crawl out, turning it inside-out like a peeled sock, often in one piece that includes the clear scale over each eye; renewing it keeps their vision sharp. Lizards shed in fragments, and frogs and salamanders eat their old skins.
Insects, spiders and crustaceans must shed their hard shell to grow. The discarded case is called the exuviae, and the new one stays soft until it hardens. Insects cannot breathe mid-moult, and the crab Ovalipes catharus must moult before mating. Most dogs shed twice yearly, guinea pigs constantly, and rabbits in spring and autumn.
Source: Moulting
