Erlinge S, Hasselquist D, Svensson M, Frodin P, Nilsson P
Animal Ecology, Department of Ecology, S-22362 Lund, Sweden e-mail:
Theoretical Ecology, Department of Ecology, S-22362 Lund, Sweden, , , , , , SE.
Oecologia. 2000 May;123(2):200-207. doi: 10.1007/s004420051006.
The reproduction of female Siberian lemmings in the increase and peak phases of the lemming cycle was investigated in connection with a ship-borne expedition along the Siberian arctic tundra. The cycle phase of each studied lemming population was determined using demographic analyses, i.e. current density indices (captured lemmings per 100 traps per 24 h), information on previous density (frequency of old lemming faeces and runways), and information from dendrochronological analyses revealing the most recent winters with a high intensity of willow-stem scarring caused by lemmings. The cycle phase determination was corroborated with data on the age profiles of the populations. The reproductive behaviour of female lemmings differed markedly in relation to cycle phase. In increase-phase populations, all captured females (including young and winter born) were reproducing (had embryos or were lactating), and females started to reproduce early in life, i.e. when <2 months old. By contrast, in peak-phase populations, only 6% of the young females and 63% of the winter-born ones were reproducing, and females did not start to reproduce until they were 5-6 months old. The average number of embryos per reproducing female was significantly higher in increase-phase populations than in peak-phase ones. It is concluded that the rapid population growth in lemmings during the increase phase can largely be explained by the early (young age) reproductive start and, consequently, the shorter generation time, the high proportion of females taking part in reproduction, and the large litters produced. Similarly, a delay in the start of reproduction, a lower proportion of reproducing females, and smaller litter sizes produced by peak-phase lemming populations can contribute substantially to the deceleration in the population increase and possibly lead to a decline.
结合一次沿西伯利亚北极苔原的船载考察，对雌性西伯利亚旅鼠在旅鼠数量周期的增长期和高峰期的繁殖情况进行了研究。通过人口统计学分析确定每个研究的旅鼠种群的周期阶段，即当前密度指数（每24小时每100个陷阱捕获的旅鼠数量）、先前密度信息（旧旅鼠粪便和跑道的频率），以及树木年代学分析提供的信息，该分析揭示了旅鼠造成柳树茎疤痕高强度的最近冬季。通过种群年龄分布数据对周期阶段的确定进行了验证。雌性旅鼠的繁殖行为在不同周期阶段有显著差异。在增长期种群中，所有捕获的雌性（包括幼体和冬季出生的）都在繁殖（有胚胎或正在哺乳），并且雌性在生命早期就开始繁殖，即小于2个月大时。相比之下，在高峰期种群中，只有6%的年轻雌性和63%的冬季出生的雌性在繁殖，并且雌性直到5 - 6个月大才开始繁殖。每个繁殖雌性的平均胚胎数在增长期种群中显著高于高峰期种群。得出的结论是，旅鼠在增长期的快速种群增长在很大程度上可以通过早期（幼年）开始繁殖来解释，因此世代时间较短、参与繁殖的雌性比例较高以及产仔数较多。同样，高峰期旅鼠种群繁殖开始延迟、繁殖雌性比例较低以及产仔数较小，可能会极大地导致种群增长减速，并可能导致种群数量下降。
