金川多肋牦牛种群调查

金川多肋牦牛中有529／6的个体具有15对肋骨，比一般牦牛多出1对，是近年来发掘出的具有独特生物学特性和优异生产性能的地方牦牛类群。弄清种群特性，将为金川多肋牦牛资源保护与利用积累基础资料。采用普查和随机抽样调查法在金川多肋牦牛分布区进行种群密度、畜群结构、繁殖率、死亡率等调查。结果显示，金川多肋牦牛分布区的牦牛密度为0．3牦牛单位／hm^2，现实载畜量为1．5羊单位／hm^2，与麦洼牦牛和甘南牦牛分布区的牦牛密度一致；畜群中适龄母牦牛比例为45．2％，母牦牛繁殖率85．9％，15对肋骨牦牛的繁殖率为90．7％，两者都显著高于其他地区牦牛；15对肋骨牦牛的繁殖率、个体终生产犊数均高于14对肋骨牦牛，且雪灾致死率前者也低于后者；金川多肋牦牛母牛的初产年龄为3岁，比一般牦牛提前一年投产；金川多肋牦牛具有种群快速增长的年龄金字塔，但受到狼害、雪灾等生态因素的强烈制约。金川多肋牦牛种群参数具有重要特异性，显示其具有较强的综合生产性能。

The Population Survey of Jinchuan Multi-rib Yak

Jinchuan yak was one kind of unique native yak population, found in recent years with special biological characteristics and better production performance. About 52 % of the Jinchuan yak population has one more pair of ribs compared with other yak populations which only have 14 pairs of ribs. This survey was to protect and utilize this yak resource better and accumulate basic data. Population density and structate of reproduction and mortality were investigated through general and random sampling survey in Jinchuan yak distribution area. According to the results,the density of Jinchuanyak was 0. 3 yak/hm2 and reality grazing capacity was 1.5 yak unit/hm2, in line with Maiwa and Gannan yak; there were 45. 2% right age female in Jinchuan yak, and the reproductive rate was 85. 9 %; those yaks with 15 pairs of ribs had a reproductive rate of 90. 7%. Both were significantly higher than other yaks（P〈0. 05）; the reproduc tive rate and individual calving number in lifetime of yak with 15 pairs of rib was higher than those with 14 pairs of ribs. However, the mortality caused by snow disaster of the former was lower than the latter; The primiparity age of Jinchuan female yak was 3 years old and one year earlier than other yaks. Jinchuan yak had a rapid growth of population age pyramid, but it was suffered from the strong restriction of ecological factors, such as wolf or snow disaster. Itis concluded that the population parameters of Jinchuan yak are distinctly different, indicating that the better performance of comprehensive production.