are thicker transverse rings, of greater length and flexion than in adults. Into adulthood, thinner horn rings force the thick transverse rings upward. Growth increment slows earlier in maturation in females than in males. Researchers use genitalia and sexual behaviour to distinguish the sexes. Females have two pairs of mammae. Hearing is sensitive and eyesight is strong—the serow is able to detect and react to movement from a distance, and it can see well in low lighting. Sense of smell is also strong, and the serow can be observed raising its head and sniffing the air around it. Distribution, ecology, and behaviour Capricornis crispus is the only wild bovine ruminant in Japan, and is endemic to three of the four main islands of Japan: primarily northern and central Honshu, and small areas in Shikoku and Kyushu. It can tolerate colder, snowier climates better than mainland serows. The animal is found solitary, in pairs, or in small family groups in open grassland and forests at an elevation of about , and uses caves to rest in. It prefers temperate deciduous forest, but also lives in broad-leaved or subalpine coniferous forest made up of Japanese beech, Japanese oak, alpine meadow, and coniferous plantations. Population density is low, at an average of , and no greater than . C. crispus is philopatric and territorial, and marks trees with sweet-sour-smelling preorbital gland secretions to indicate its territory. Males and females establish separate, overlapping ranges, typically , but the male's is typically larger than the female's. Aggression is rare, but the serow may react with hostility to territorial breaches. Due to the extinction of its once-primary predator, the Japanese wolf, the Japanese black bear is its only predator. It flees with a whistling snort when it detects danger. It is an agile, sure-footed mountain dweller that is able to sprint up mountains and to jump from cliff to cliff to safety; hunters have likened this display of agility to the ninja. The diurnal Japanese serow is a browser that feeds in early morning and late afternoon, primarily on fleshy or coniferous leaves, plant shoots, and acorns. It feeds on alder, sedge, Japanese witch-hazel (Hamamelis japonica), and Japanese cedar. It adjusts its diet to what food is locally available, and, as a ruminant, the serow has a four-chambered stomach. Studies indicate that even severe winters have a negligible impact on the serow's food intake, suggesting that,