Via reddit, today I learned a lot about antlers. Did you know that reindeer is the only species of deer for which both males and females grow antlers? And that in many species of moose, the longer the antler, the better the corresponding hearing? This and more from this fascinating Wikipedia article:
First, the origin of the word “antler”:
Antler comes from the Old French antoillier (from ant-, meaning before, oeil, meaning eye and -ier, a suffix indicating an action or state of being) possibly from some form of an unattested Latin word *anteocularis, “before the eye” (and applied to the word for “branch” or “horn“).
And then on the occurrence and function of antlers:
Antlers are unique to cervids and found mostly on males: only reindeer have antlers on the females, and these are normally smaller than those of the males. Nevertheless, fertile does from other species of deer have the capacity to produce antlers on occasion, usually due to increased testosterone levels.The pronghorn’s “horns” fit some of the criteria of antlers, although are not considered true antlers because they contain keratin.
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. Antlers are considered one of the most exaggerated cases of male secondary sexual traits in the animal kingdom,and grow faster than any other mammal bone. Growth occurs at the tip, and is initially cartilage, which is later replaced by bone tissue. Once the antler has achieved its full size, the velvet is lost and the antler’s bone dies. This dead bone structure is the mature antler. In most cases, the bone at the base is destroyed by osteoclasts and the antlers fall off at some point. As a result of their fast growth rate, antlers are considered a handicap since there is an incredible nutritional demand on deer to re-grow antlers annually, and thus can be honest signals of metabolic efficiency and food gathering capability.
In most arctic and temperate-zone species, antler growth and shedding is annual, and is controlled by the length of daylight. Although the antlers are regrown each year, their size varies with the age of the animal in many species, increasing annually over several years before reaching maximum size. In tropical species, antlers may be shed at any time of year, and in some species such as the sambar, antlers last several years. Some equatorial deer never shed their antlers. Antlers function as weapons in combats between males, which sometimes cause serious wounds, and as dominance and sexual displays.
The ancestors of deer had tusks (long upper canine teeth). Antlers appear to replace tusks; two modern species, the musk deer and the water deer, have tusks and no antlers, the muntjac has small tusks and small antlers, and other deer have full-sized antlers and no tusks.The diversification of antlers, body size and tusks has been strongly influenced by changes in habitat and behavior (fighting and mating).
Reindeer use their antlers to clear away snow so they can eat the vegetation underneath. This is one possible reason that females of this species evolved antlers. Another possible reason is for female competition during winter foraging.
In moose, antlers appear to act as large hearing aids. Moose with antlers have far more sensitive hearing than moose without, and a study of trophy antlers with an artificial ear confirmed that the antler behaves like a parabolic reflector.