Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON, Canada.
Oecologia. 2012 Mar;168(3):601-20. doi: 10.1007/s00442-011-2120-z. Epub 2011 Sep 25.
We review the population dynamics of red-backed voles (Myodes species) in North America, the main deciduous and coniferous forest-dwelling microtines on this continent, and compare and contrast their pattern with that of the same or similar species in Eurasia. We identify 7 long-term studies of population changes in Myodes in North America. Using autoregressive and spectral analysis, we found that only 2 of the 7 show 3- to 5-year cycles like those found in some Eurasian populations. There was no relationship between latitude and cycling. The general lack of cyclicity is associated with two key aspects of their demography that act in tandem: first, poor overwinter survival in most years; second, chronically low densities, with irregular outbreak years. Eight factors might explain why some Myodes populations fluctuate in cycles and others fluctuate irregularly, and we review the evidence for each factor: food supplies, nutrients, predation, interspecific competition, disease, weather, spacing behavior and interactive effects. Of these eight, only food supplies appear to be sufficient to explain the differences between cyclic and non-cyclic populations. Irregular fluctuations are the result of pulsed food supplies in the form of berry crops (M. rutilus) or tree seeds (M. gapperi) linked to weather patterns. We argue that, to understand the cause for the patterns in the respective hemispheres, we must know the mechanism(s) driving population change and this must be linked to rigorous field tests. We suggest that a large-scale, year-round feeding experiment should improve overwintering survival, increase standing densities, and flip non-cyclic Myodes populations into cyclic dynamics that would mimic the patterns seen in the cyclic populations found in parts of Eurasia.
我们回顾了北美的红背田鼠（Myodes 种）的种群动态，这是该大陆主要的落叶林和针叶林栖息的小型哺乳动物，并将其模式与欧亚大陆相同或相似物种的模式进行了比较和对比。我们确定了北美 7 项关于 Myodes 种群变化的长期研究。使用自回归和频谱分析，我们发现只有 7 项中的 2 项显示出 3 到 5 年的周期，与一些欧亚大陆种群中的周期相似。周期与纬度之间没有关系。一般来说，缺乏周期性与它们的两个关键人口统计学特征有关：首先，大多数年份的越冬存活率都很差；其次，密度长期处于低位，爆发年份不规则。有八个因素可能解释为什么一些 Myodes 种群呈周期性波动，而另一些种群呈不规则波动，我们回顾了每个因素的证据：食物供应、营养、捕食、种间竞争、疾病、天气、空间行为和相互作用。在这八个因素中，只有食物供应似乎足以解释周期性和非周期性种群之间的差异。不规则波动是浆果作物（M. rutilus）或树木种子（M. gapperi）形式的脉冲食物供应与天气模式相关的结果。我们认为，要了解各自半球模式的原因，我们必须了解驱动种群变化的机制，这必须与严格的现场测试联系起来。我们建议进行大规模的、全年的喂养实验，以提高越冬存活率、增加种群密度，并将非周期性的 Myodes 种群转变为类似欧亚大陆部分地区周期性种群的周期性动态。
