An antler-less ancestor
The Korean water deer (Hydropotes inermis argyropus) represents an early branch of the deer family tree. Unlike nearly all other members of the family Cervidae, males do not grow antlers. Instead, they possess a more primitive feature: elongated upper canine teeth that grow into sharp tusks. These saber-like fangs are a relic from antlerless, tusked ancestors that lived millions of years ago. While female water deer have very small canines, a male's tusks are formidable weapons, averaging 5.5 centimeters (2.2 inches) in length and capable of reaching up to 8 centimeters (3.1 inches). The teeth erupt when the deer is about six to seven months old and are fully developed by the age of two.
These tusks are not fixed in place. The deer can control their position with facial muscles, drawing them backward when eating. This anatomical detail distinguishes them from many other mammals with large canines. The deer's skull structure supports these unique teeth, which are used exclusively for combat between territorial males. Gyeonggi Province, with its mix of wetlands, river basins and low hills, provides an ideal habitat for these animals, which prefer areas with tall reeds and grasses for cover. South Korea hosts an estimated 700,000 water deer, making it the world's largest population and a unique location for observing this evolutionary divergence.
A life of solitary combat
Water deer are solitary and highly territorial. During the rut, which occurs from November to December, males engage in fierce fights to control territory and access to females. The combatants stand parallel to each other and swing their heads downward, attempting to slash at the neck, shoulders, and back of their rival with their tusks. These fights are often bloody and can result in serious wounds, with tufts of hair and strips of skin torn away. Unlike pushing contests of antlered deer, these encounters are swift and dangerous. The loser signals submission by laying its head and neck on the ground or by fleeing the territory.
Males mark their territories using several methods. They create dung piles, rub their foreheads on trees, and bite off vegetation to delineate their boundaries. They are also the only members of the deer family to possess inguinal glands in their groin, which are used for scent marking. Communication includes a range of sounds. The most common is a harsh bark used as an alarm call. During the rut, males also produce a unique clicking sound, possibly with their molar teeth, and a soft squeak when courting females. When injured or in distress, they can emit a screaming wail.