Abstract
It is 100 years since the first paper described the multiannual cycles
in Arctic rodents and lagomorphs. The mechanisms driving population
cycles in animals like lemmings and voles are complex, often attributed
to extrinsic factors, such as food availability and quality, pathogens,
parasites and/or predators. While extrinsic factors provide insights
into population cycles, none fully explain the phenomenon. We propose an
underlying innate, intrinsic mechanism, based on epigenetic regulation,
that drives population cycles under harsh arctic conditions. We propose
that epigenetically driven phenotypic changes associated with sexual
development, growth, and behaviour accumulate over time in offspring,
eventually producing a phase change from rising population density to
eventual population collapse. Under this hypothesis, and unlike previous
hypotheses, extrinsic factors would modify population cycles but would
not be primary drivers. The interaction between our intrinsic cycle and
extrinsic factors explains established phenomena like delayed-density
dependence, whereby population growth is controlled by time-dependent
negative feedback. We advocate for integrating a century of field
research with the latest epigenetic analysis to better understand the
drivers of population cycles.