The bristles surrounding the tusks of a walrus that often give it a "moustached" look are called vibrissae.
Picture from NY Times
There can be anywhere from 400 to 700 vibrissae in a row, usually 13 to 15 rows surrounding the tusks. Though they are usually fairly short in order to avoid getting in the way of eating, the vibrissae can be up to a foot long. The vibrissae are attached to muscles and are supplied with blood and nerves, making them highly sensitive organs.