Caribou, water, and ice – fine-scale movements of a migratory arctic ungulate in the context of climate change

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.

Observed and predicted effects of climate change on Arctic caribou and reindeer

“…Some, such as the Dolphin and Union population and Peary caribou, migrate across the sea ice between seasonal ranges (Miller et al 1977;Poole et al 2010), whereas others prefer moving across frozen lakes and rivers for ease and directional persistence of movement and increased visibility of predators (Pruitt 1959;Sharma et al 2009;Leblond et al 2016). Warming surface temperatures will, and already are, changing the annual timing of both sea ice (Poole et al 2010) and freshwater ice (Latifovic and Pouliot 2007;Sharma and Magnuson 2014) formation and break-up.…”

“…They reported that caribou tended to select ice and avoided water when crossing or moving near large water bodies and that ice increased caribou movement rates. Simulations predicted that for the Rivière-aux-Feuilles herd as much as 36% of ice crossings during the spring and fall migrations could be lost by 2070 (Leblond et al 2016). Loss of ice crossings would likely increase the distance travelled during migrations because the migratory path would skirt water bodies rather than cross them (Leblond et al 2016), thereby increasing the energetic cost of migration.…”

“…Although they tend to avoid water during migration (Leblond et al 2016;Fullman et al 2017), caribou are adept swimmers (Miller 1995;Avgar et al 2013). Based on behavioural observations, they are likely familiar with breaking through thin ice and are certainly able to survive these events (Miller and Gunn 1986).…”

“…A reduction in the availability of ice suitable for movement (i.e., ice that can support the weight of caribou or reindeer) along the migratory paths of Rangifer populations, or conversely an increase in thin ice and open water, could have deleterious consequences for migratory behaviour. For example, Leblond et al (2016) studied the influence of ice on the movements of caribou of the Rivière-aux-Feuilles herd in northern Québec, Canada. They reported that caribou tended to select ice and avoided water when crossing or moving near large water bodies and that ice increased caribou movement rates.…”

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

“…Some species such as the Arctic fox have specialized into using the seasonal sea ice as a foraging platform (Lai et al 2015) and can travel thousands of kilometres over land and ice (Tarroux et al 2010). Migrating caribou in northern Quebec regularly cross large lakes when they are frozen (Leblond et al 2016), and spring ice breakup is a critical time when impassable barriers, such as flooded rivers, can arise even for strong swimmers like caribou. Ice cover may thus have important impacts on daily movements, seasonal migrations, and dispersal events of tundra wildlife, with far-reaching consequences on their foraging behavior, population dynamics, and species distributions.…”