Lemming winter habitat choice: a snow-fencing experiment

Abstract

The insulative value of early and deep winter snow is thought to enhance winter reproduction and survival by arctic lemmings (Lemmus and Dicrostonyx spp). This leads to the general hypothesis that landscapes with persistently low lemming population densities, or low amplitude population fluctuations, have a low proportion of the land base with deep snow. We experimentally tested a component of this hypothesis, that snow depth influences habitat choice, at three Canadian Arctic sites: Bylot Island, Nunavut; Herschel Island, Yukon; Komakuk Beach, Yukon. We used snow fencing to enhance snow depth on 9-ha tundra habitats, and measured the intensity of winter use of these and control areas by counting rodent winter nests in spring. At all three sites, the density of winter nests increased in treated areas compared to control areas after the treatment, and remained higher on treated areas during the treatment. The treatment was relaxed at one site, and winter nest density returned to pre-treatment levels. The rodents' proportional use of treated areas compared to adjacent control areas increased and remained higher during the treatment. At two of three sites, lemmings and voles showed significant attraction to the areas of deepest snow accumulation closest to the fences. The strength of the treatment effect appeared to depend on how quickly the ground level temperature regime became stable in autumn, coincident with snow depths near the hiemal threshold. Our results provide strong support for the hypothesis that snow depth is a primary determinant of winter habitat choice by tundra lemmings and voles.

Climate change and the ecology and evolution of Arctic vertebrates

“…Many parts of the Arctic receive less than 40 cm of snowfall during a winter, but this is often redistributed heavily by wind, creating a mosaic of habitat patches differing substantially in snow depth, with snow being trapped by topography and vegetation. A recent manipulation experiment that altered snow cover showed that increasing the snow depth in marginal winter habitat increased habitat use by small mammals in these areas, as expected, but the impact on demography (reproductive rate or mortality due to predation) was less clear 14 . Nonetheless, it is likely that change in snow depth or snow quality (e.g., increased amount of wet snow, icing, or collapses in the subnivean spaces, which increase the energetic costs incurred in getting access to food plants or in severe instances totally obstruct access) caused by climate warming will have a strong impact on small mammal population dynamics.…”

“…The distribution of their winter nests show a strong association with deeper snow, and the greatest probability of occurrence is at snow depths from 60 to 120 cm 12,13 . A deep, dry snow cover reduces thermal stress on small mammals that overwinter in subnivean spaces, most notably by dampening the daily temperature fluctuations that they experience 12,14 . Many parts of the Arctic receive less than 40 cm of snowfall during a winter, but this is often redistributed heavily by wind, creating a mosaic of habitat patches differing substantially in snow depth, with snow being trapped by topography and vegetation.…”

Effects of changing permafrost and snow conditions on tundra wildlife: critical places and times

“…Domine et al (2016a) showed at Bylot Island, in the Canadian High Arctic, that the highest snowpack thermal resistances were found in drifts and in willow shrubs, thus explaining quantitatively their suitability as a habitat for subnivean life. The temperature under deep snow is both higher and less fluctuating than under shallow snow (Duchesne et al 2011;Reid et al 2012), and temperature stability better predicts lemming presence than temperature per se (Duchesne et al 2011).…”

“…The insulating properties of the snowpack are determined by its thickness and thermal conductivity. Collared lemmings (Dicrostonyx groenlandicus) and brown lemmings (Lemmus trimucronatus) studied in the High Arctic prefer areas with a snowpack ≥60 cm (Duchesne et al 2011) and are very apt at finding snow drifts (usually called snowbeds by ecologists; Reid et al 2012), often located on the leeward side of slopes or terrain with a rugged microtopography (Duchesne et al 2011) or in habitats where erect shrubs capture drifting snow. Although these areas may occupy a small proportion of the landscape, they are critical for the winter survival of these species.…”

Demographic response of tundra small mammals to a snow fencing experiment

“…We used rows of snow fence on large grids (> 7 ha) to trap drifting snow during winter. In a previous paper, we showed that our manipulation increased snow depth on the experimental grids, created a more favourable sub‐nivean temperature regime and influenced the spatial distribution of lemming and vole winter nests (Reid et al 2012). Therefore, our manipulation improved the winter habitat quality of small mammals.…”