the skull by the time the animal is a year old. The pedicel gives rise to a spiky antler the following year, that is replaced by a branched antler in the third year. This process of losing a set of antlers to develop a larger and more branched set continues for the rest of the life. The antlers emerge as soft tissues (known as velvet antlers) and progressively harden into bony structures (known as hard antlers), following mineralisation and blockage of blood vessels in the tissue, from the tip to the base. Antlers might be one of the most exaggerated male secondary sexual characteristics, and are intended primarily for reproductive success through sexual selection and for combat. The tines (forks) on the antlers create grooves that allow another male's antlers to lock into place. This allows the males to wrestle without risking injury to the face. Antlers are correlated to an individual's position in the social hierarchy and its behaviour. For instance, the heavier the antlers, the higher the individual's status in the social hierarchy, and the greater the delay in shedding the antlers; males with larger antlers tend to be more aggressive and dominant over others. Antlers can be an honest signal of genetic quality; males with larger antlers relative to body size tend to have increased resistance to pathogens and higher reproductive capacity. In elk in Yellowstone National Park, antlers also provide protection against predation by wolves. Homology of tines, that is, the branching structure of antlers among species, have been discussed before the 1900s. Recently, a new method to describe the branching structure of antlers and determining homology of tines was developed. Teeth Most deer bear 32 teeth; the corresponding dental formula is: . The elk and the reindeer may be exceptions, as they may retain their upper canines and thus have 34 teeth (dental formula: ). The Chinese water deer, tufted deer, and muntjac have enlarged upper canine teeth forming sharp tusks, while other species often lack upper canines altogether. The cheek teeth of deer have crescent ridges of enamel, which enable them to grind a wide variety of vegetation. The teeth of deer are adapted to feeding on vegetation, and like other ruminants, they lack upper incisors, instead having a tough pad at the front of their upper jaw. Biology Diet Deer are browsers, and feed primarily on foliage of grasses, sedges, forbs, shrubs and