The sight of a domestic sheep being shorn is familiar, but wild species, such as the North American Bighorn or the European Mouflon, do not require this intervention for survival. Domesticated breeds have been intentionally bred over millennia to produce continuously growing fiber, making annual shearing a necessity for their health. The answer lies in the fundamental biological differences between the coats of wild sheep, which are genetically designed to self-manage, and their domesticated relatives.
The Biological Difference: Hair vs. Wool Coats
The coat of a wild sheep is known as a double coat, consisting of two types of fiber. The outer layer is composed of long, coarse guard hairs called kemp, which provide protection from the elements and physical hazards. Beneath this layer lies a finer, softer undercoat of woolly fibers that offers insulation.
Crucially, the fibers in this double coat have a terminal growth pattern, meaning they grow to a specific length before naturally stopping. This growth cycle is similar to that of most other mammals, where hair is shed and replaced seasonally. Domesticated wool sheep, particularly breeds like the Merino, were selectively bred to lose this terminal growth, resulting in a fleece of fine, highly crimped fibers that grow continuously.
How Wild Sheep Naturally Manage Their Fleece
Wild sheep manage their coat through a natural process called molting. This seasonal shedding is triggered by environmental cues, primarily the increasing daylight hours of spring, which initiate hormonal changes that detach the old winter coat from the skin.
The thick, heavy winter coat loosens and begins to “blow out” as temperatures rise, typically in the late spring or early summer months. This process is essential for the sheep to regulate its body temperature and prevent overheating.
Wild sheep also actively participate in coat removal by rubbing their bodies against rough surfaces like rocks, tree trunks, and dense bushes. This physical action helps pull the masses of dead fiber away from the body. The shedding allows them to maintain agility and easily navigate the rugged, mountainous terrain they inhabit.
Why Domesticated Breeds Must Be Shorn
The need for shearing in domesticated sheep is a direct consequence of thousands of years of selective breeding. Early breeders valued denser, longer-staple wool and intentionally selected for animals that had lost the natural shedding gene. This genetic manipulation resulted in a fleece that never stops growing and remains attached to the animal year-round.
If a domesticated sheep is not shorn annually, the continuously growing wool can lead to severe health complications:
- The heavy fleece traps heat, causing the animal to overheat in warm weather.
- Extreme wool growth impedes mobility and can lead to “wool blindness” when the fleece grows over the eyes.
- A long, dense, unshorn fleece creates an ideal habitat for parasites and bacteria.
- Soiled wool around the hindquarters attracts flies that lay eggs, a condition known as flystrike.
Shearing is a necessary management practice for these domesticated breeds to maintain hygiene and prevent fatal infections.