260px|thumb|A [[dragonfly in its radical final moult, metamorphosing from an aquatic nymph to a winged adult.]]
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.
In medieval times, it was also known as "mewing" (from the French verb "muer", to moult), a term that lives on in the name of Britain's Royal Mews where the King's hawks used to be kept during moulting time before becoming horse stables after Tudor times.
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.
Examples
{| class="wikitable sortable"
|-
! Group
! Item shed
! Timing
! Notes
|-
| Cats
| Fur
| Usually around spring-summer time
| Cats moult fur around spring-summer time to get rid of their "winter coat". Cats have thicker fur during the colder winter months to keep them warm, then around spring and summer they shed some of their fur to get a thinner coat for the warmer summer months. Some cats need brushing during moulting, since dead hairs can get trapped in the cat's fur.
|-
| Dogs and other canids
| Fur
| Semi-annually, spring and fall (autumn).
| Moulting or shedding in canids, as in all mammals, is due to fluctuations in the amount of melatonin secreted by their pineal gland in response to seasonal sunlight variations rather than temperature variations. This seasonality in moulting is most preserved in Arctic breeds of dogs which shed twice each year whereas most other breeds moult once each year.
|-
| Chickens
| Feathers
| Usually autumn (non-commercial hens).
| Chickens generally stop laying eggs when their moulting begins and recommence laying when their new feathers have re-grown.
|-
| Mallards
| Feathers
| Mid-summer - early fall
| After the end of the breeding season, most mallards moult their flight feathers. As the brightly coloured breeding plumage of the males leaves them vulnerable to predation, they lose it through moulting, replacing it with eclipse plumage that aids in camouflage until their flight feathers regrow, upon which they moult again and regain their breeding colours.
|-
| Snakes
| Skin
| Regularly, when old skin is outgrown.
| Snakes rub against rough surfaces to assist removal of their shed skin.
|-
| Lizards
| Skin
| Regularly, when old skin is outgrown.
| Lizards, like snakes, rub against objects to help remove their shed skin and then consume the shed skin for calcium and other nutrients.
|-
| Amphibians
| Skin
| Regularly.
| Salamanders and frogs shed their skins regularly, then often eat it.
|-
| Hermit crabs
| Exoskeleton
| Regularly, when the carapace is outgrown.
| Land hermit crabs bury themselves for many weeks while they moult and then consume their exoskeleton.
|-
| Arachnids
| Exoskeleton
| Regularly, when the exoskeleton is outgrown.
| Arachnids moult regularly to grow, often becoming reclusive and fasting for long periods prior to a moult.
|-
| Insects
| Exoskeleton
| Regularly in larvae, when the exoskeleton is outgrown.
| In species with a "complete" metamorphosis, the final moult transforms the body, typically from a soft-bodied larva to a reproductive, winged and sometimes colourful adult. In mayflies, a winged subimago moults one last time to a winged adult.
|}
In birds
{| class="wikitable" style="float:right; width:360px; margin-left:5px;"
|-
| 180px|Loggerhead shrike moulting.
| 200px|Loggerhead shrike with normal plumage.
|-
| colspan="2" style="text-align:center;"|<small>A loggerhead shrike in mid-moult (left) and with regular plumage (right).</small>
|}
thumb|A juvenile [[king penguin moulting out its brown chick down and growing its first dark grey and white adult feathers]]
In birds, moulting is the periodic replacement of feathers by shedding old feathers while producing new ones. Feathers are dead structures at maturity which are gradually abraded and need to be replaced. Adult birds moult at least once a year, although many moult twice and a few three times each year. <!-- "In a nutshell, species that follow the Complex Alternate Strategy have two moults per year as an adult and three moults in their first year of life (also called their first plumage-cycle)." - from Chipping Sparrow article -->
The process of moulting in birds is as follows: First, the bird begins to shed some old feathers, then pin feathers grow in to replace the old feathers. As the pin feathers become full feathers, other feathers are shed. This is a cyclical process that occurs in many phases. It is usually symmetrical, with feather loss equal on each side of the body. Because feathers make up 4–12% of a bird's body weight, it takes a large amount of energy to replace them.
Determining the process birds go through during moult can be useful in understanding breeding, migration and foraging strategies. One non-invasive method of studying moult in birds is through using field photography. The evolutionary and ecological forces driving moult can also be investigated using intrinsic markers such as stable hydrogen isotope (δ2H) analysis. In some tropical birds, such as the common bulbul, breeding seasonality is weak at the population level, instead moult can show high seasonality with individuals probably under strong selection to match moult with peak environmental conditions.
A 2023 paleontological analysis concluded that moulting probably evolved late in the evolutionary lineage of birds.
Forced moulting
In some countries, flocks of commercial layer hens are force-moulted to reinvigorate egg-laying. This usually involves complete withdrawal of their food and sometimes water for 7–14 days or up to 28 days under experimental conditions,
In arthropods
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. This process is called ecdysis. Most Arthropoda with soft, flexible skins also undergo ecdysis. Ecdysis permits metamorphosis, the sometimes radical difference between the morphology of successive instars.
A new skin can replace structures, such as by providing new external lenses for eyes. The new exoskeleton is initially soft but hardens after the moulting of the old exoskeleton. The old exoskeleton is called an exuviae<!--yes, this looks like a plural, but it's correct-->. While moulting, insects cannot breathe. In the crustacean Ovalipes catharus moulting must occur before they mate.
In dogs
Most dogs moult twice each year, in the spring and autumn, depending on the breed, environment and temperature. Dogs shedding much more than usual are known as "blow coats" or "blowing coats".
In guinea pigs, hamsters and rabbits
Most guinea pigs moult constantly, whereas hamsters shed less frequently, and rabbits experience seasonal moulting in spring and autumn. The moulting process in small mammals is influenced by seasonality, hormones, and overall health. In hamsters, excessive shedding may indicate stress or disease. A balanced diet and regular grooming are essential for maintaining a healthy coat.
Gallery
<gallery>
File:Molting yellow-eyed penguin IMG 6073.jpg|A moulting yellow-eyed penguin
File:Ranapipiensmoulting.jpg|A leopard frog moulting and eating the skin
File:Extatosoma tiaratum - Crawling out of skin.jpg|Giant prickly stick insect crawling out of his moulted skin
File:SnakeSkin.JPG|Moulted snake skin
File:Balcan Green Lizard 2.JPG|Moulting European green lizard
File:Grasshopper moult 2015-08-04.jpg|Discarded moult of a grasshopper (Caelifera)
File:Cicada Final Molt and Darkening timelapse 14 2021-05-27.webm|A cicada moulting
File:Shed Tiliqua rugosa skin, 5 cm scale.jpg|Moult of a Tiliqua rugosa lizard, 5 cm scale bar
</gallery>
See also
- Abscission – a more general term for when an organism sheds parts of itself
References
External links
- Moulting in Pigeons
- Moulting in Chicken and other fowl
de:Häutung