The interplay between seasonality and density: consequences for female breeding decisions in a small cyclic herbivore

Abstract

BackgroundCyclic rodent population dynamics are subjected to both intrinsic regulatory processes such as density-dependence and extrinsic environmental forcing. Among extrinsic factors, seasonal environmental variation is understood to facilitate cycles. In rodents, these processes have been studied mostly independently and their relative importance for population dynamics is poorly known.ResultsWe performed a detailed analysis of common vole (Microtus arvalis) reproduction in a cyclic population using a spatially extensive data set over 17 years in central-western France. Environmental seasonality was the main source of explained variation in common vole reproduction. Additionally, inter-annual variation in the environment explained a smaller part of the variance in reproduction in spring and summer than in winter, whereas the effect of density was only found in autumn and winter. In particular, we detected a strong impact of plant productivity on fecundity during the breeding season, with low vegetation productivity being able to bring vole reproduction nearly to a halt. In contrast, vole reproduction during autumn and winter was mainly shaped by intrinsic factors, with only the longer and heavier females being able to reproduce. The effect of population density on reproduction was negative, mediated by direct negative effects on the proportion of breeders in autumn and winter during outbreak years and by a delayed negative effect on litter size the following year.ConclusionsDuring the main breeding season, variability of female vole reproduction is predominantly shaped by food resources, suggesting that only highly productive environment may induce vole outbreaks. During fall and winter, variability of female vole reproduction is mainly controlled by intrinsic factors, with high population density suppressing reproduction. This suggests, in this cyclic population, that negative direct density dependence on reproduction could explain winter declines after outbreaks.

Small rodent population cycles and plants – after 70 years, where do we go?

“…Several assumptions related to this hypothesis have never been tested. In particular, only a handful of studies have linked increased availability of presumed high‐quality food items to actual ingestion of those foods (Janova, Heroldova & Cepelka, 2016) and consequently increased reproduction rates (but see Sullivan & Sullivan, 2014; Pinot, Gauffre & Bretagnolle, 2014). While there is no question that food quality does affect a range of aspects of herbivore health (e.g.…”

Population density does not affect seasonal regulation of reproductive physiology in male water voles

“…In common voles and meadow voles, it has been shown that density has a direct impact on reproduction [17,18]. Indeed, during phases of high density, reproduction decreases in these voles leading to stabilization of the population.…”

Fluctuating Asymmetry and Population Dynamics of the Common Shrew, Sorex araneus, in Central Siberia under Climate Change Conditions

“…Population cycle is commonly observed in the regions with the stable climate and overpopulation is assumed as a limiting factor for a population growth. In this case, peak abundance is accompanied by low breeding success [5][6][7][8]. Developmental stability, which can be estimated by fluctuating asymmetry of morphological characters, is another population parameter.…”