Pelage
| pelage [ˈpelij] the fur, hair, or wool of a mammal ========== Hairs grow out of pits in the skin called follicles. The base of the hair, buried in the skin, is called the root and the visible part of the hair is called the shaft. Many hairs are paired with what are called "arrector pili muscles". These microscopic muscles, under the direction of the autonomic nervous system, allow hairs to contract and relax - aiding biothermal (temperature) regulation. These muscles also come into play during times of stress, with hairs "standing on end" when frightened or angry, and can often make the animal appear larger than it really is. Types Guard Guard hairs overlay the insulating fur and protect it. When you look at the coat of a furred animal, what you see, for the most part, is its guard hairs. Did you know that a porcupine's quills are actually highly-modified guard hairs? Guard hairs consist of three major components - the inner layer is called the medulla, the mid layer is called the cortex and the outer layer is called the cuticle. The cortex, or mid layer, determines the pigment, or colour, of the hair while the outer layer presents variable cuticle scale patterns. Under magnification, every mammal species' guard hairs look different from another mammal species' guard hairs. This uniqueness allows wildlife conservation officers to determine, via forensic observation, whether hunters are breaking laws or not. Some mammals' guard hairs do not have a medulla, just a cuticle and cortex. In flying squirrels, the medulla fills most of the shaft! Guard hairs on the same animal can vary greatly in colour and thickness. Insulating Insulating hair, or underfur, is shorter, much more densely packed and much finer than guard hair. The hair, by itself, does not serve to insulate. Insulation is acheived by the air layers that are trapped by the insulating fur. As discussed above, the arrector pili muscles will contract when the animal is cold, which in turn makes the insulating hairs "stand up", thereby allowing the trapping of yet more air for greater insulation against the cold. Vibrissae See vibrissae Colouration  Colouration is determined by a group of proteins called melanins - there are two chemically distinct forms - the brown-to-black eumelanins and the yellow-to-reddish pheomelanins. Genes determine the quantity and quality of the melanins produced by each individual animal, therefore, the pelage of North American flying squirrels can vary greatly in colouration. This variation occurs on every scale, from sub-specie to familial level. There are also seasonal variations in colouration present in some geographic regions, for instance, some southern flying squirrels' upper toe fur will turn white in winter. A flying squirrels' pelage is great camouflage for life in the trees. At right is a great example of how pelage colouration can vary in flying squirrels. (Photo courtesy J. Vecoli) Dorsal Generally, the colour of the dorsal fur (body and tail) in both species is mid-brown, but can be tinged with grey, pink, cinnnamon, light brown and olive shades, and black. Ventral Ventral fur colour (body and tail) is always off-white or cream coloured. Closer inspection of the ventral belly fur can usually distinguish the southern from the northern species. In northern flying squirrels, ventral fur turns from the off-white to cream colouration to a slate grey colour before the hair shaft meets the epidermis. In southern flying squirrels, the ventral fur remains a constant off-white to cream colour along the hair shaft length. Patagium The patagium is covered with short guard hairs - this is an adaptation that allows for minimal air resistance, or aerodynamic drag. The patagium edge is ringed along the outside with black-coloured fur. Molting Molting is nature's way of renewing an old, worn and damaged body covering. Southern flying squirrels molt twice per year, once in spring and again in late summer/early fall. The spring molt is only a partial molt, of the head and neck area only. According to Nancy Wells, "males and non-lactating females start the process first; lactating females undergo the parital molt after their spring litters are three to six weeks old". The fall coat is generally thicker and more robust than the spring coat. The northern flying squirrel molts but once per year, in late summer/early fall. Molting times vary quite a bit, and are subject to genetics and latitude, amongst other variables. The time it takes to complete a molt, from head to toe, can be anywhere from three to six weeks. Captive flyers' molting times will deviate somewhat from the molting times of wild flyers. Juveniles of both species possess what is called the "juvenile pelage", but it differs only in subtle colourations from the final adult product, unlike, for example, the juvenile pelage of a fawn, whose pelage differs markedly from its adult form. The juvenile's tail is nowhere near as thick and lustrous as the adult's tail, and is dark on the underside - a stark contrast to the cream colour of the adult tail's underside. The molting process always begins at the nose and works back towards the tail. The molting process also places energy demands on the animals, but food is generally plentiful during molt times. |