These hairs are usually long, straight, and stiff. Their bases are well-supplied with nerves, and vibrissae are very sensitive to touch. They provide the animal with information about its immediate surroundings. Vibrissae are usually restricted to certain parts of the body and are often found in tufts or clumps. We are all familiar with the whiskers on the face of a dog, but perhaps less aware that vibrissae may occur on other parts of the body as well, for example, on the ankles of a squirrel or the rump of some crevice-roosting bats.
Most hair is shed periodically in a process called molt .
Molt may take place continuously, with a few hairs being replaced at any time, as in humans. More commonly, molt is restricted to certain seasons of the year or certain times of an animal's life, at which times all hairs are replaced. Molts that take place during development are also very common. In modern mammals, hair serves to insulate, to conceal, to signal, to protect, and to sense the immediate surroundings. Insulation serves to conserve heat, but also, as in the case of diurnal desert animals such as the camel, to protect against excessive heat.