Population cycles and changes in body size of the lynx in Alaska
Population cycles and changes in body size of the lynx in Alaska
复制标题
阿拉斯加山猫的种群周期和体型变化
作者：
Y. Yom;S. Yom;D. Macdonald;E. Yom
猞猁加拿大猞猁是北美北方森林中常见的捕食者。它的种群在9到11年的周期内波动，与它的主要猎物——美洲雪蹄兔的种群规模同步。利用成人博物馆的标本，我们研究了20世纪下半叶阿拉斯加猞猁的头骨（和身体）大小的变化。阿拉斯加的人口周期平均为9年，与邻近的育空地区相似。利用猞猁的收获数据作为种群规模的估计，我们发现头骨大小与种群规模呈负相关。这种关系在死亡年(X)的种群密度中表现得最强烈，但在X-3年，这是生命第一年（或几年）的一种结转效应，表明快速生长时期的条件决定了体型。我们认为，这种密度依赖效应可能是由于食物供应的变化，要么是竞争的不利影响，要么是食物供应的可能减少。在20世纪下半叶，两个颅骨参数显著下降。我们不知道年份效应的原因，并认为这可能是由于猎物可获得性的长期变化。在研究期间，犬的大小没有变化，这可能表明在整个研究期间，雪鞋兔保持了其作为猞猁主要猎物的地位。
The lynx Lynx canadensis is a common predator in the boreal forests of North America. Its population fluctuates during a 9- to 11-year cycle in synchrony with the population size of its main prey, the snowshoe hare Lepus americanus. Using adult museum specimens, we studied changes in skull (and hence body) size of the lynx in Alaska during the second half of the 20th century. The population cycle in Alaska averaged 9 years, similar to that reported in the neighbouring Yukon. Using harvest data of lynx as an estimate of population size, we found that skull size was negatively related to population size. This relationship was strongest not for the population density in the year of death (X), but for year X-3, a carry-over effect from the first year (or years) of life, indicating that conditions during the fast-growth years are determining body size. We suggest that the density-dependent effect is probably due to changes in food supply, either resulting from the adverse effects of competition or a possible diminished availability of food. Two skull parameters decreased significantly during the second half of the 20th century. We do not know the cause for the year effect and suggest that it might be due to a long-term change in the availability of prey. Canine size did not change during the study period, probably an indication that snowshoe hares maintained their status as the main prey of the lynx throughout the study period.