Mammals will shed their fur for several reasons. A common reason for mammals to shed is discarding old or damaged hair strands to make way for new fur. Depending on their health and species, mammals may lose a minimal amount of hair or large amounts. However, loss of hair is not always a good sign since stress, malnutrition and health issues can cause mammals to lose hair. The presence of lice and fleas may produce bald patches in a mammal's fur coat.
A snake's skin does not grow during its growth spurts, which makes it necessary for snakes to shed their skin. Snakes initiate the shedding process by rubbing their mouths and noses on the ground until its skin is pushed up. Once their skins push up, snakes wriggle back and forth and eventually crawl out of their old skins. Juvenile snakes shed more frequently than older snakes since the growth process slows down as snakes mature. Young snakes usually shed every four to five weeks, while more mature snakes may only need to shed two to three times a year.
Fish do not shed scales naturally. Any loss is usually the result of an injury. Fish are able to regenerate loss scales. All lost scales are replaced at the same time. New scales do not display growth rings that were on the lost scales. Growth rings are natural rings on a fish which shows the specimen's age, similar to the rings found in tree trunks. Once a year passes, though, the new scales show their own growth rings.
Molting is the process of birds shedding their old feathers and replacing them with new ones. Birds never molt all their feathers at the same time. Most birds molt feathers one wing at a time to maintain their flight capabilities. However, some ducks and swans molt all their flight feathers at the same time, rendering them flightless for several weeks until their new feathers mature. Birds have two molting periods, in the fall and spring. In the spring, male birds molt old feathers and replace them with new, brightly colored feathers to attract mates,