DOI: 10.5061/dryad.684s1
title: Data from: Using experimentation to understand the 10-year snowshoe hare cycle in the boreal forest of North America

description: 1. Population cycles have long fascinated ecologists from the time of
 Charles Elton in the 1920s. The discovery of large population fluctuations
 in undisturbed ecosystems challenged the idea that pristine nature was in
 a state of balance. The 10-year cycle of snowshoe hares (Lepus americanus
 Erxleben) across the boreal forests of Canada and Alaska is a classic
 cycle, recognized by fur traders for more than 300 years. 2. Since the
 1930s ecologists have investigated the mechanisms that might cause these
 cycles. Proposed causal mechanisms have varied from sunspots to food
 supplies, parasites, diseases, predation, and social behaviour. Both the
 birth rate and the death rate change dramatically over the cycle. Social
 behaviour was eliminated as a possible cause because snowshoe hares are
 not territorial and do not commit infanticide. 3. Since the 1960s
 large-scale manipulative experiments have been used to discover the major
 limiting factors. Food supply and predation quickly became recognized as
 potential key factors causing the cycle. Experiments adding food and
 restricting predator access to field populations have been decisive in
 pinpointing predation as the key mechanism causing these fluctuations. 4.
 The immediate cause of death of most snowshoe hares is predation by a
 variety of predators, including the Canada lynx (Lynx canadensis Kerr).
 The collapse in the reproductive rate is not due to food shortage as was
 originally thought, but is a result of chronic stress from predator
 chases. 5. Five major issues remain unresolved. First, what is the nature
 of the predator-induced memory that results in the prolonged low phase of
 the cycle? Second, why do hare cycles form a travelling wave, starting in
 the centre of the boreal forest in Saskatchewan and travelling across
 western Canada and Alaska? Third, why does the amplitude of the cycle vary
 greatly from one cycle to the next in the same area? Fourth, do the same
 mechanisms of population limitation apply to snowshoe hares in eastern
 North American or in similar ecosystems across Siberia? Finally, what
 effect will climatic warming have on all the above issues? The answers to
 these questions remain for future generations of biologists to determine.
description: 1_Metadata for Kluane
 Hare GridsDescriptive data for the
 data given in the following 5 files2_Phases of Hare
 CycleDescribes the phases of
 the ten-year cycle of snowshoe hares for the years of study in the
 Yukon3_Monitoring Data for
 Small MammalsThe detailed data for
 the 3 main species discussed in this paper for the years studied,
 population size and confidence limits.4_Controls Hare Live
 trap data KluaneThe detailed demographic
 data for snowshoe hares on the control grids by capture date over all the
 years of study and all the grids that were controls.5_Feeding Experiment
 Data Figure 1The data used in Figure
 1 for the feeding experiment on hares.6_Fence+Food Hare
 Capture DataThe detailed demographic
 data for the 1986-96 fence and food individual snowshoe hares by capture
 time, for this experiment that has been critical for our
 understanding.