Timing of population peaks of Norway lemming in relation to atmospheric pressure: A hypothesis to explain the spatial synchrony.

Vidar Selås

doi:10.1038/srep27225

Abstract

Herbivore cycles are often synchronized over larger areas than what could be explained by dispersal. In Norway, the 3–4 year lemming cycle usually show no more than a one-year time lag between different regions, despite distances of up to 1000 km. If important food plants are forced to reallocate defensive proteins in years with high seed production, spatially synchronized herbivore outbreaks may be due to climate-synchronized peaks in flowering. Because lemming peaks are expected to occur one year after a flowering peak, and the formation of flower buds is induced in the year before flowering, a two-year time lag between flower-inducing climate events and lemming peaks is predicted. At Hardangervidda, South Norway, the probability that a year was a population peak year of lemming during 1920–2014 increased with increasing midsummer atmospheric pressure two years earlier, even when the number of years since the previous peak was accounted for.

Highlights

Herbivore cycles are often synchronized over larger areas than what could be explained by dispersal
There is no doubt that predators may depress rodent numbers in the decline phase of the cycle[2], or that small rodents in peak years may reduce the biomass of food plants[3], but these patterns would be expected if rodent cycles are generated by fluctuations in food quality, caused by factors other than herbivory[4]
The probability of a year being a lemming peak year increased with the number of years elapsed since the previous peak (χ2 = 17.10, P < 0.001) and with atmospheric pressure 16–30 June two years earlier

Summary

Introduction

Herbivore cycles are often synchronized over larger areas than what could be explained by dispersal. In Norway, the 3–4 year lemming cycle usually show no more than a one-year time lag between different regions, despite distances of up to 1000 km. If important food plants are forced to reallocate defensive proteins in years with high seed production, spatially synchronized herbivore outbreaks may be due to climate-synchronized peaks in flowering. In Norway, population peaks of lemming usually show no more than a one-year time lag between different regions, despite distances of up to 1000 km[17]. They are commonly synchronised with population peaks of other small rodents[18]. Correspondence and requests for materials should be addressed to V.S. (email: vidar.selas@ nmbu.no) www.nature.com/scientificreports/

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