A1 Refereed original research article in a scientific journal
REPRODUCTIVE INVESTMENT UNDER FLUCTUATING PREDATION RISK - MICROTINE RODENTS AND SMALL MUSTELIDS
Authors: KORPIMAKI E, NORRDAHL K, VALKAMA J
Publisher: CHAPMAN HALL LTD
Publication year: 1994
Journal: Evolutionary Ecology
Journal name in source: EVOLUTIONARY ECOLOGY
Journal acronym: EVOL ECOL
Volume: 8
Issue: 4
First page : 357
Last page: 368
Number of pages: 12
ISSN: 0269-7653
DOI: https://doi.org/10.1007/BF01238188
Abstract
We studied the reproductive investment of microtine rodents (bank vole (Clethrionomys glareolus), Microtus epiroticus and Microtus agrestis) in western Finland under predation risk from small mustelids. During 1984-1992, the yearly mean litter size of overwintered bank voles was smaller at high least weasel and stoat densities than at low densities (close to 3 versus 4-5). In addition, the annual mean litter size of young bank voles was negatively correlated to the least weasel density. In young M. agrestis voles, the yearly late summer litter size was negatively associated with the autumn density of small mustelids. In the crash phase of the vole cycle (1989 and 1992), we removed small mustelids (mainly least weasels) from four unfenced areas in late April to late May and studied the reproduction of voles in four removal and comparable control areas (each 2-4 km2). Reduction of small mustelids significantly increased the proportion of pregnant bank vole females, but not that of pregnant Microtus vole females. We conclude that predation risk apparently reduced reproductive investment of free-living bank vole females; these voles appear to trade their current parental investment against future survival and reproductive prospects. Accordingly, the presence of small mustelids (or their scent) may slow down the reproductive rate of voles. As antipredatory behaviours occurred on a large scale, our results add evidence to the hypothesis that crashes in multiannual vole cycles are driven by small mustelid predators.
We studied the reproductive investment of microtine rodents (bank vole (Clethrionomys glareolus), Microtus epiroticus and Microtus agrestis) in western Finland under predation risk from small mustelids. During 1984-1992, the yearly mean litter size of overwintered bank voles was smaller at high least weasel and stoat densities than at low densities (close to 3 versus 4-5). In addition, the annual mean litter size of young bank voles was negatively correlated to the least weasel density. In young M. agrestis voles, the yearly late summer litter size was negatively associated with the autumn density of small mustelids. In the crash phase of the vole cycle (1989 and 1992), we removed small mustelids (mainly least weasels) from four unfenced areas in late April to late May and studied the reproduction of voles in four removal and comparable control areas (each 2-4 km2). Reduction of small mustelids significantly increased the proportion of pregnant bank vole females, but not that of pregnant Microtus vole females. We conclude that predation risk apparently reduced reproductive investment of free-living bank vole females; these voles appear to trade their current parental investment against future survival and reproductive prospects. Accordingly, the presence of small mustelids (or their scent) may slow down the reproductive rate of voles. As antipredatory behaviours occurred on a large scale, our results add evidence to the hypothesis that crashes in multiannual vole cycles are driven by small mustelid predators.
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