Antlers are the usually large and complex horn-like appendages of most deer species, mostly worn by males only, for some species such as caribou by both sexes. They consist of bony outgrowths from the head with no covering of keratin as is found in true horns. Each antler grows from an attachment point on the skull called a pedicle. While an antler is growing it is covered with highly vascular skin called velvet, which supplies oxygen and nutrients to the growing bone; once the antler has achieved its proper size, the velvet is lost and the antler's bone dies. This dead bone structure is the mature antler. Antlers shed after each mating season.
An advancer, among hunters, is one of the starts or branches of a buck's attire between the back antler and the palm (the flattened part of the antlers). In other words, it is the second branch of a buck's horn.
Antlers appear to act as large hearing aids. This effect was discovered by researchers George and Peter Bubenik and published the findings in the European Journal of Wildlife in March 2008. Moose with antlers have far more sensitive hearing than moose without. The pair then studied trophy antlers with an artificial ear, confirming the discovery of the effects on hearing by acting as a parabolic reflector.