Coastal habitat use by ringed seals Pusa hispida following a regional sea-ice collapse: importance of glacial refugia in a changing Arctic

Declines in Arctic sea ice are predicted to have large consequences for Arctic marine mammals. To study the consequences of a sudden collapse in sea ice in 2006 within Svalbard (Norway), 38 ringed seals Pusa hispida were equipped with Satellite Relay Data Loggers in the period 2010-2012; the behaviour of these seals was then compared with data collected during deployments of similar equipment on 22 ringed seals in 2002-2003, prior to the sea-ice collapse. In the present study, statistical models were used to investigate whether the altered sea-ice regime modified movement patterns or foraging behaviour in coastal areas. All seals in these areas concentrated their time close to tidal glacier fronts. However, seasonally resident individuals (immature seals) spent less time close to glacier fronts when in the fjords, than year-round coastal residents (mature seals), likely due to competitive exclusion of the younger animals in these key feeding and resting habitats. Movements and space use became restricted in winter due to formation of land-fast ice. This spatial restriction was delayed and less extreme in 2010-2012, consistent with the late formation and limited extent of land-fast ice in this period. Ringed seals in 2010-2012 also made longer dives, surface intervals between dives were shorter, and increased proportions of the dives were spent descending, with decreased proportions of time at the bottom of dives compared to 2002-2003, indicating increased foraging effort. Further sea-ice deterioration and retreat of glacier fronts are predicted for Svalbard, which are likely to increase intraspecific competition and affect ringed seal distribution, reproductive success and abundance.