Population cycles in voles and lemmings: state of the science and future directions

Abstract

Despite nearly a century of research, the causes of population cycles in Arvicoline rodents (voles and lemmings) in northern latitudes are not yet fully understood. Theory tells us that delayed density‐dependent feedback mechanisms are essential for rodent population cycles, suggesting vegetation–rodent, rodent–parasite or rodent–predator interactions as the most likely drivers of population cycles. However, food provisioning, carried out either indirectly through fertilisation treatments of the habitat or directly through food supplementation, has failed to alter population cycles substantially, suggesting that variation in food supply by itself is not necessary or sufficient to cause cyclic fluctuations in abundance. Predator exclusion experiments conducted in Fennoscandia have succeeded in slowing population crashes and increasing autumn densities, implicating predation as the most likely cause of rodent cycles in this region. However, experimental removal of specialist predators in northern England had no discernible effect on a cyclic vole population, casting doubt on the notion that predation is a necessary explanation of rodent population cycles. Population cycle research has contributed substantially to our current understanding of the dynamics, regulation and persistence of biological populations, but we do not yet know with certainty what factors or processes cause multiannual population fluctuations or if population cycles are driven by the same mechanisms everywhere. Recent theoretical and empirical studies suggest that extrinsic factors (primarily food supply and predator abundance) may interact with population intrinsic processes (e.g. dispersal, social behaviour, stress response) to cause multiannual population fluctuations and to explain biological attributes of rodent population cycles. Solving the enigma of population cycles may necessitate identifying factors and processes that cause phase‐specific demographic changes and performing conclusive experiments to ascertain the mechanisms that generate multiannual density fluctuations.

Demography of snowshoe hare population cycles

“…Population cycles are essentially demographic processes, and cannot be fully understood or explained without first understanding demographic mechanisms that underlie cyclic changes in abundance (Oli andDobson 1999, Krebs 2002). Despite seven decades of theoretical and empirical research, a thorough demographic characterization of snowshoe hare population cycles grounded in observational or experimental data had not been performed, and our understanding demographic mechanisms underlying cyclic changes in abundance remained incomplete until now (Barraquand et al 2017).…”

“…Through a combination of parameters of statistically rigorous capture–recapture modeling framework and 40 yr of field data on the same population, our study fills the aforementioned knowledge gaps by (1) providing the first rigorous, empirically based demographic characterization of the rates of population change that must be explained; (2) providing evidence that the demography of snowshoe hare cycles showed a repeatable pattern over five population cycles; (3) discerning demographic mechanisms underlying the increase, peak, and decline phases; and (4) explaining the variation in peak densities achieved by the same population across different cycles. Cyclic mammals inhabit variety of habitats across northern hemisphere and exhibit diverse life histories, but they all show similar dynamical patterns (Krebs , Myers , Oli ). Similar analyses of other cyclic mammal populations would help us understand whether or to what extent cyclic mammalian populations are demographically similar.…”

“…Cyclic fluctuations in abundance exhibited by some terrestrial mammals in northern latitudes, commonly called “population cycles,” are considered to be one of nature’s greatest mysteries (Keith , Stenseth , Myers , Oli ). Cyclic mammals often are the most important herbivores in terms of biomass and impact across trophic levels, and their cyclic population dynamics are thought to be key processes in the structure and function of ecosystems where they occur (Krebs et al , Ims and Fuglei , Schmidt et al ).…”

Hypotheses and models linking epigenetic transgenerational effects to population dynamics: Exploring oscillations and applications to wildlife cycles

“…Many European moths oscillate with cycles in the 8-10-yr range (e.g., Cerrato et al (2019)). This could be indicative of very strong environmental signals in this range, Microtines 3 -5 0.33 -0.5 3.3 -5.5 (Hansen et al, 1999); (Hanski et al, 2001); (Oli, 2019); (Stenseth et al, 2003 such as the North Atlantic Oscillation. It could also indicate a mixture of maternal and grandmaternal epigenetic programming.…”

Large-Scale Vole Population Synchrony in Central Europe Revealed by Kestrel Breeding Performance

“…For instance, while predators are likely to be a key factor for vole population synchrony in southeastern Norway (Ims and Andreassen, 2000), they hardly have any effect on vole populations in northern England (Petty et al, 2000;Graham and Lambin, 2002). As a consequence, it is necessary to study population synchrony at different locations and spatial scales if we want to reach a comprehensive understanding of mechanisms driving population dynamics (Oli, 2019).…”