英语介绍牦牛

yak 英[jæk] 美[jæk] n. 牦牛; 笑话; vi. <非正，贬>没完没了地谈些无关要紧的事，喋喋不休，唠叨; [例句]The influence of capability of Yak hairs treated with different plasma was studied.研究了各等离子体参数对牦牛毛纤维性能的影响。[其他] 第三人称单数：yaks 复数：yaks 现在分词：yakking 过去式：yakked过去分词：yakked

yak/ Poёphagus grunniens

YAKThe dark black-brown coat is dense, wooly, and extremely shaggy, although the colour is variable in domestic yaks. 'Golden' wild yaks are also known, but are extremely rare. The shoulders are high and humped, with a broad, drooping head. The short legs have broad hooves and large dewclaws as an adaptation to mountainous environments. The horns are found in both sexes, though those of the females are considerably smaller and shorter. They grow up to 51 cm / 20 inches long in females, and 95 cm / 38 inches in males. The curved horns grow out from the sides of the head and curve upwards. Ontogeny and Reproduction Gestation Period: 258 days Young per Birth: 1 every other year.Weaning: About 1 year. Sexual Maturity: By 6 years. Life span: 23 years. The mating season begins in September, lasting for several weeks in which bulls fight each other for females. Young are born in June, the season of plenty in the Tibetan plateau. Ecology and Behavior Due to the scarcity of vegetation in their habitat, wild yaks must travel great distances in order to obtain sufficient nourishment. In July, there is a general downward shift from the high plateaus to the lower plains, where mosses and swamp vegetation are at their peak. As the temperature rises in August, the herds head back up to the plateaus, even retiring to snowy regions to beat the heat. Although sensitive to warm temperatures, wild yaks can easily tolerate temperatures of -40o C/F. In severe cold, they have been seen bathing in lakes and streams. Generally distrustful, if a herd is disturbed they will flee for a long distance, galloping with their tails held erect. If something unexpected appears in their flight path, yaks will bluff, attacking with a fast charge and normally stopping just 10-20 meters / 30-60 feet away from the intruder. In spite of their bulky, awkward appearance, yaks are excellent, sure-footed climbers. One of the few vocalizations is a loud grunt, made during the breeding season by wild yaks. Domestic yaks, however, "grunt" throughout the year - hence the specific name grunniens. Family group: Herds of 10-200 individuals consisting of females and young, adult males solitary or in bachelor groups with up to 12 members. Diet: Lichens, grasses, and tubers. Main Predators: Tibetan wolf.

The wild yak has a dense undercoat of soft, close-matted hair which is covered by generally dark brown to black outer hair. Its long, shaggy coat reaches almost to the ground. The wild yak can weigh up to 1000 kg (2200 lb) with a shoulder height of over 2 m (6.5'). It occurs in treeless uplands, including plains, hills, and mountains, from as low as 3200 m (10,500') up to the limit of vegetation at about 5400 m (18,000'). It stays in high areas with permanent snow during the warmer months of August and September, and spends the rest of the year at lower elevations. The wild yak grazes on grasses, herbs and lichens. Ordinarily it gathers in groups of 10 - 30 or more, but it may occasionally be observed in large groups of 100 - 200. The wild yak was once numerous and widespread on the entire Tibetan plateau north of the Himalayas. Currently it is found in remote areas of the Tibetan plateau and adjacent highlands, including Gansu Province, China, with a few having been observed in the Chang Chenmo Valley of Ladakh (eastern Kashmir, India). Wild yak distribution is highly clumped, with most animals in widely scattered herds, concentrated in the areas with little disturbance by humans. A survey conducted in 2003 found increasing populations of wild yak compared to previous surveys taken 10 years earlier. Uncontrolled hunting by natives and military personnel is the main reason for the wild yak's decline. Its range has been reduced by more than half during this century. Poaching remains the main current threat. The wild yak has lost most of the best alpine meadow and steppe habitat to pastoralists. Problems are also caused by habitat disturbance, hybridization and competition with domestic yaks, and disease transmitted by domestic yaks.