Abstract
BackgroundFreshwater lakes and rivers of the Northern Hemisphere have been freezing increasingly later and thawing increasingly earlier during the last century. With reduced temporal periods during which ice conditions are favourable for locomotion, freshwater bodies could become impediments to the inter-patch movements, dispersion, or migration of terrestrial animals that use ice-covered lakes and rivers to move across their range. Studying the fine-scale responses of individuals to broad-scale changes in ice availability and phenology would help to understand how animals react to ongoing climate change, and contribute to the conservation and management of endangered species living in northern environments. Between 2007 and 2014, we equipped 96 migratory caribou Rangifer tarandus caribou from the Rivière-aux-Feuilles herd in northern Québec (Canada) with GPS telemetry collars and studied their space use. We measured contemporary (digital MODIS maps updated every 8 days, 2000–2014) and historical (annual observations, 1947–1985) variations in freshwater-ice availability and evaluated the concurrent responses of caribou to these changes.ResultsIce had a positive influence on caribou movement rates and directionality, and caribou selected ice and avoided water when moving across or in the vicinity of large water bodies. When ice was unavailable, caribou rarely swam across (6 % of crossings) and frequently circumvented water bodies for several km. Although ice phenology did not change significantly during our study, climate projections indicated that ice availability could decrease considerably before the end of the century, generating a ~28 % increase in distance travelled by caribou during the early spring and fall migrations.ConclusionsWe demonstrated that ice availability influenced the movements of a migratory arctic ungulate. Warmer air temperatures in the Arctic will undoubtedly modify the phenology of ice forming on freshwater lakes and rivers. If migratory caribou are unable to adjust the timing of their migrations, they could be forced to circumvent unfrozen water bodies more frequently and over broader areas, which may increase the distance, time, and energy they use to reach wintering areas. The long-term conservation of wide-ranging species will ultimately depend on our ability to identify the fine-scale behavioural reactions of individuals to broad-scale changes in climate and land use.Electronic supplementary materialThe online version of this article (doi:10.1186/s40462-016-0079-4) contains supplementary material, which is available to authorized users.
Highlights
Freshwater lakes and rivers of the Northern Hemisphere have been freezing increasingly later and thawing increasingly earlier during the last century
We studied the responses of migratory caribou (Rangifer tarandus caribou) to trends in the availability of ice on lakes and rivers in an Arctic/subarctic region to assess potential mechanisms linking fine-scale individual behaviour to broad-scale climatic conditions
Breakup dates of the largest lakes used by migratory caribou and Lake Nichicun were related to the North Atlantic Oscillation (NAO) in May, whereas their freeze dates were related to the NAO in October and the Arctic Oscillation (AO) in September
Summary
Freshwater lakes and rivers of the Northern Hemisphere have been freezing increasingly later and thawing increasingly earlier during the last century. Studying the fine-scale responses of individuals to broad-scale changes in ice availability and phenology would help to understand how animals react to ongoing climate change, and contribute to the conservation and management of endangered species living in northern environments. Magnuson et al [18] analyzed time series of ice extents on water bodies of the Northern Hemisphere and found that lakes and rivers had increasingly earlier breakup and later freezing dates during the 1846–1995 period These seasonal processes may influence nonpagophilic terrestrial species that use ice on inland water bodies to move across their range or colonize new areas [20, 21] by impeding their movements [22], altering the timing of their migrations [23], or increasing their risks of drowning [21]
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