Moulting

In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is a process by which an animal casts off parts of its body to serve some beneficial purpose, either at specific times of the year, or at specific points in its life cycle.

Moulting can involve shedding the epidermis (skin), pelage (hair, feathers, fur, wool), or other external layer.

In some groups, other body parts may be shed, for example, the entire exoskeleton in arthropods, including the wings in some insects.

The bird must retain sufficient feathers to regulate its body temperature and repel moisture.

[5] Some species of bird become flightless during an annual "wing moult" and must seek a protected habitat with a reliable food supply during that time.

[5] Because feathers make up 4–12% of a bird's body weight, it takes a large amount of energy to replace them.

[9] The evolutionary and ecological forces driving moult can also be investigated using intrinsic markers such as stable hydrogen isotope (δ2H) analysis.

[11] A 2023 paleontological analysis concluded that moulting probably evolved late in the evolutionary lineage of birds.

This causes a body weight loss of 25 to 35%,[14] which stimulates the hen to lose her feathers, but also reinvigorates egg-production.

[18] In arthropods, such as insects, arachnids and crustaceans, moulting is the shedding of the exoskeleton, which is often called its shell, typically to let the organism grow.

Most dogs moult twice each year, in the spring and autumn, depending on the breed, environment and temperature.