Migration phenology of beluga whales in a changing Arctic

Abstract

Global warming has been linked to dramatic environmental changes, particularly in polar marine environments, where water temperatures and sea-ice cover are especially affected. Using satellite telemetry, we investigated how local changes in sea-surface temperatures (2002−2004) affected the movement patterns of belugas Delphinapterus leucas in eastern Hudson Bay (EHB), Canada. Of 26 whales equipped with satellite transmitters, 17 had records that extended beyond the summer season and showed a fall migration pattern. During summer, foraging activity of individuals was either aggregated, at small spatial scales of <90 km (Strategy A), or dispersed, at larger spatial scales of >120 km (Strategy D). In 2002 and 2003, belugas preferentially selected cold water temperatures <4°C, while, in 2004, no selection occurred. In 2002−2003, the range of water temperatures was larger than in 2004. Moreover, while cold waters were found mainly to the north of the Belcher Islands in 2002–2003, cold waters were broadly scattered throughout the whole bay in 2004. Independent of year, animals employing Strategy A left their summer habitat late (31 October, ±14 d), while those using Strategy D left about 3 wk earlier (4 October, ±2 d). In 2002−2003, the range of water temperatures was larger than in 2004. Moreover, while cold waters were found mainly to the north of the Belcher Islands in 2002–2003, cold waters were broadly scattered throughout the whole bay in 2004. Therefore, it appeared that the strategy used in summer, and hence the migration timing among EHB belugas, was related to sea-surface temperature conditions. Although other factors may also trigger migration, the present study is among the first to reveal a relationship between environmental conditions and habitat use and the migration patterns of beluga whales. Consequently, this work indicates alterations in a well-established migration phenology due to longer term effects of climate change on this Arctic species.