Moulting is the way in which some animals change or renew a part of their body in a specific time of the year or of their lives.
This phenomenon can happen to mammals, insects, birds or reptiles. For example dogs lose part of their hair during the warmest periods of the year. The old hair is replaced by a new one, which is lighter.
Birds also change their feathers according to the temperature and also when they reach maturity. Sometimes, moulting causes other change in their behaviour, for example hens stop laying eggs for a while before moulting.
Some reptiles, like snakes, change their skin when this has become too old and has grown too much. They rub their head against a hard object like a rock and they manage to remove it all after a while.
A similar moulting happens to amphibians too.
Arthropods, like insects, spiders or crabs, change their exoskeleton or shell when they are growing.
In fact, the exoskeleton is not like the skin, it’s fixed and it does not grow. So when the animal has started to grow, it has to change its exoskeleton which will give them a more comfortable shell.
Also humans change their skin, although it doesn’t happen as clearly as for other animals. We do lose some skin when we have a shower for example, or when we scratch. It’s a natural process and it helps keeping our body healthy.