Sika, Shansi sika, Spotted deer, Japanese deer
The Sika deer, also known as the Spotted deer or the Japanese deer, is a species of deer native to much of East Asia and introduced to various other parts of the world. Sika deer are either small or medium-sized, depending on where they live. They all have a very small head and short legs. The males' antlers generally have three or four points on them, though some with a more dominant role have more. Females have two black bumps on their head instead. Sika deer are yellow-brown to reddish-brown, and they have a dark dorsal stripe which is surrounded in the summer by white spots. During winter, their color is dark gray to black with no spots or just very faint ones.
Sika deer are natives of Eastern Asia and Japan and have also been introduced to other regions of the world, including Europe, North America, Australia, New Zealand, and the Philippines. They are mainly forest-dwelling deer and they prefer forested areas that have a dense understory. However, they can adapt well to a range of other habitats like freshwater marshes (in Maryland State, Eastern US) and grasslands (in New Zealand).
Primarily crepuscular or nocturnal, sika deer sometimes forage during the day, either singly or in small groups. In addition, these deer are not especially gregarious. Adult males remain solitary most of the year though they sometimes group together, while females with their fawns form groups of 2 or 3 only during the birthing season. Males mark their territorial boundaries by digging holes using their forefeet and antlers. When territorial disputes between males occur, hooves and antlers are used as the main weapons. Sika deer are excellent swimmers and will readily enter the water in order to escape from predators or for other reasons.
Sika deer are polygynous and a male can successfully gather up to 12 females within his territory during the mating season, which is in autumn (September and October). A single fawn is born in May or June following a gestation period of about 30 weeks. When a fawn is born, the mother hides her baby in thick undergrowth. The young stays very quiet and still while it waits for the mother to return. Surprisingly, fawns have almost no smell, and even hunting dogs cannot detect their scent. When fawns are a few weeks old they venture out to play with the other fawns. The newborn is nursed up to 10 months with increasingly fatty milk. It becomes independent 10 to 12 months after birth and attains reproductive maturity at 16 to 18 months of age.
The main threats to Sika deer include water pollution, habitat loss, and hunting for their meat, as well as their antler velvet, which has a use in traditional medicines. Loss of genetic diversity due to fragmentation of their habitat is also a cause for concern, as well as competition with goats and other feral animals. Another threat is collisions with vehicles. Hybridization with native red deer in places like the United Kingdom is a conservation risk, threatening the genetic integrity of both species.
Japan has the largest Sika deer population in the world with 3,080,000 individuals as of 2015 estimation by the Japanese Ministry of the Environment. It is still increasing due to conservation efforts and the extinction of its main predator, the Grey wolf, over a century ago. There are also relatively small native populations in Russia (8,500-9,000 individuals) and China (less than 1,000 individuals).
Sika deer are important to control native vegetation by browsing, and they are large prey for their native predators.