Guard hair

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

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.

[1][2][3] Bristles are firm, generally long hairs in equids and bovids, some carnivorans, etc., that grow continuously and form manes.

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.

Spines are the stiff, enlarged guard hairs that exhibit definitive growth and form the protective quills of echidnas, hedgehogs and especially porcupines.