Abstract
There is increasing concern over how Arctic fauna will adapt to climate related changes in sea-ice. We used long-term sighting and genetic data on beluga whales (Delphinapterus leucas) in conjunction with multi-decadal patterns of sea-ice in the Pacific Arctic to investigate the influence of sea-ice on spring migration and summer residency patterns. Substantial variations in sea-ice conditions were detected across seasons, years and sub-regions, revealing ice–ocean dynamics more complex than Arctic-wide trends suggest. This variation contrasted with a highly consistent pattern of migration and residency by several populations, indicating that belugas can accommodate widely varying sea-ice conditions to perpetuate philopatry to coastal migration destinations. However, a number of anomalous migration and residency events were detected and coincided with anomalous ice years, and in one case with an increase in killer whale (Orcinus orca) sightings and reported predation on beluga whales. The behavioural shifts were likely driven by changing sea-ice and associated changes in resource dispersion and predation risk. Continued reductions in sea-ice may result in increased predation at key aggregation areas and shifts in beluga whale behaviour with implications for population viability, ecosystem structure and the subsistence cultures that rely on them.
Highlights
Declines in Arctic sea-ice are arguably the most dramatic evidence of the effects of current climate warming on ocean systems
We addressed two specific questions: (i) how does the pattern of annual return to a particular coastal area correlate with interannual variation in sea-ice and (ii) do anomalies in beluga migration behaviour correlate with sea-ice anomalies?
This study revealed that beluga whales are resilient to widely varying ice conditions while perpetuating philopatry each year to discrete coastal locations and suggests that reaching these areas at this time of year is critical
Summary
Declines in Arctic sea-ice are arguably the most dramatic evidence of the effects of current climate warming on ocean systems. How such declines reverberate through marine ecosystems is largely unknown [1]. In upper trophic level (UTL) species the first discernible effects of changing sea-ice will likely be behavioural either by directly altering ranging patterns [2,3] or indirectly by influencing resource (food, mates, breeding sites) and risk (e.g. predation) dispersion. We assess the relationship between changing sea-ice and beluga whale migration and summer residency patterns of a number of populations over two decades of dramatic sea-ice changes in the Pacific Arctic. Genetic and telemetry studies have identified several discrete populations that follow traditional migratory routes between wintering areas and summering grounds where belugas feed, moult and raise their young
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