Bunch T D, Hoefs M, Glaze R L, Ellsworth H S
J Wildl Dis. 1984 Apr;20(2):125-33. doi: 10.7589/0090-3558-20.2.125.
The prevalence of horn aberrations in Dall's sheep from the Kluane Lake area of Yukon Territory observed during July 1982 represented 1% of the total population and 7% of rams 6 yr or older. Ewes were not considered in these percentages because they were too difficult to inspect by aerial survey. When these data were combined with other data collected from 1977 through 1981, the prevalence equalled 2.4% of the total population and slightly exceeded 16% in mature rams (greater than or equal to 6 yr). The anomaly followed necrosis of the terminal region of the horn core and the sequestering of portions of the core within the sheath as the sheath continued to grow. Sheath that was produced after the core was anatomically altered resulted in abnormal growth patterns of the horn. Rams with aberrant horns could not maintain homeostatic temperatures within horn cores when horns were experimentally exposed to -80 C for 30 min. Histologic examination of superficial and cornual vascular systems did not reveal any structural alterations that would restrict blood flow within cores of affected horns. Examination of museum specimens consisting of 130 skulls from rams and 81 from ewes collected from Alaska, USA, Yukon Territory, Canada, and Northwest Territories, Canada, established only one ewe and no rams with the horn aberration. The skull was from a ewe and had both horns affected and was collected from the Joe River Drainage, Yukon Territory in 1912.
1982年7月在育空地区克卢恩湖地区观察到的多尔大角羊的角畸变率，在总种群中占1%，在6岁及以上的公羊中占7%。这些百分比未将母羊计算在内，因为通过航空调查检查母羊太难了。当这些数据与1977年至1981年收集的其他数据相结合时，畸变率在总种群中为2.4%，在成年公羊（大于或等于6岁）中略超过16%。这种异常情况是在角芯末端区域坏死以及随着角鞘继续生长，角芯部分在鞘内被隔离之后出现的。角芯在解剖学上发生改变后产生的角鞘导致了角的异常生长模式。当实验中将角暴露在-80摄氏度下30分钟时，有异常角的公羊无法在角芯内维持体内平衡温度。对角的表面和角部血管系统的组织学检查未发现任何会限制受影响角芯内血流的结构改变。对博物馆标本的检查包括从美国阿拉斯加、加拿大育空地区和加拿大西北地区收集的130个公羊头骨和81个母羊头骨，仅发现一只母羊有角畸变，公羊未发现。该头骨来自一只母羊，两只角均受影响，于1912年从育空地区的乔河排水区采集。
