Down Awn and guard hairs of cat 2012 11 13 9203r

Guard hair or overhair is the outer layer of

hair Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and ...

of most

mammals A mammal () is a vertebrate animal of the class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three middle e ...

, which overlay the fur. Guard hairs are long and coarse and protect the rest of the pelage (fur) from abrasion and frequently from moisture. They are visible on the surface of the fur and usually lend a characteristic contour and color pattern. Underneath the contour hair is the short, dense, fine down. There are three types of guard hair: awns, bristles, and spines.G. A. Feldhamer, J. F. Merritt, C. Krajewski, J. L. Rachlow, K. M. Stewart. ''Mammalogy: Adaptation, Diversity, Ecology. Fifth Edition.''

Johns Hopkins University Press Johns Hopkins University Press (also referred to as JHU Press or JHUP) is the publishing division of Johns Hopkins University. It was founded in 1878 and is the oldest continuously running university press in the United States. The press publi ...

. 2020Robert E. Martin, Ronald H. Pine, Anthony F. DeBlase. ''A Manual of Mammalogy: With Keys to Families of the World''. 3rd edition. Waveland Pr Inc. 2011D. A. Kelt, J. L. Patton. ''A Manual of the Mammalia: An Homage to Lawlor’s “Handbook to the Orders and Families of Living Mammals”.''

University of Chicago Press The University of Chicago Press is the university press of the University of Chicago, a Private university, private research university in Chicago, Illinois. It is the largest and one of the oldest university presses in the United States. It pu ...

. 2020

Description

Guard hair (overhair) is the top or outer layer of the coat. Guard hairs are longer, generally coarser, and have nearly straight shafts that protrude through the layer of softer down hair. The distal end of the guard hair is the visible layer of most mammal coats. The guard hair is spread over most of the skin, constitutes the main mass of the fur, and gives the contour and color of the fur, from the combinations in different percentages of two pigments: brown and black eumelanin, and yellow and red pheomelanin. This layer has the most marked pigmentation and gloss, manifesting as coat markings that are adapted for

camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the b ...

or display. Guard hair repels water and blocks sunlight, protecting the undercoat and skin in wet or aquatic habitats, and from the sun's

ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

radiation. Guard hairs can also reduce the severity of cuts or scratches to the skin. Many mammals, such as the domestic dog and cat, have a pilomotor reflex that raises their guard hairs as part of a threat display when agitated.

Types of guard hair

The three major types of guard hair recognized are awns, spines and bristles, although intermediates between these types are known.

Awn

Awn hair Awn hairs are the intermediate hairs in a mammal's coat. They are shorter than the guard hairs and longer than the down hairs. They help with insulation and protect the down hairs underneath. Most of the visible coat is made of this kind of hair ...

is the most common type of guard hair, characterized by an expanded distal end, a thin base, and definitive growth. The shafts of the awn are thick and usually spindle-shaped (or blade- or shieldlike), thinning gradually at the tip. Spindle-shaped portion is hard and usually differently colored. Awns usually lie in one direction, giving the pelage a distinct contour. This type of hair is found in

carnivorans Carnivora ( ) is an Order (biology), order of Placentalia, placental mammals specialized primarily in eating flesh, whose members are formally referred to as carnivorans. The order Carnivora is the sixth largest order of mammals, comprising at ...

. In equids,

cattle Cattle (''Bos taurus'') are large, domesticated, bovid ungulates widely kept as livestock. They are prominent modern members of the subfamily Bovinae and the most widespread species of the genus '' Bos''. Mature female cattle are calle ...

, and on the face and legs of

sheep Sheep (: sheep) or domestic sheep (''Ovis aries'') are a domesticated, ruminant mammal typically kept as livestock. Although the term ''sheep'' can apply to other species in the genus '' Ovis'', in everyday usage it almost always refers to d ...

, the covering bristles are shorter, stiffer, straighter, and inconspicuously spindled.

Bristles

Bristles are firm, generally long hairs in equids and bovids, some carnivorans, etc., that grow continuously and form manes. The mane often varies by sex, serving to distinguish the sexes (

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

). For example, male lions have a collar of long, hard outline hair that grows continuously and extends to the shoulders and forms a mane on the back of the neck. Bristles function as visual signals that augment facial expressions (e.g., lions) or body postures (e.g.,

horses The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 milli ...

Spines

The guard hairs are sometimes modified to form defensive spines. Spines are the stiff, enlarged guard hairs that exhibit definitive growth and form the protective quills of echidnas, hedgehogs and especially

porcupines Porcupines are large rodents with coats of sharp Spine (zoology), spines, or quills, that protect them against predation. The term covers two Family (biology), families of animals: the Old World porcupines of the family Hystricidae, and the New ...

. In porcupines, the cuticular scales are elongate and form barbs that make it difficult to remove imbedded spines.

References

{{Reflist Mammal anatomy