Bowhead whales spend more time in waters with colder sea surface temperatures

Marine mammals are under potential threats due to rapid ocean warming. Such threats may be especially challenging for the bowhead whale (Balaena mysticetus), an endemic arctic cetacean, because it is limited in how much further north it can go. To explore the effects of global warming on this species, data from 84 bowhead whales in Baffin Bay – West Greenland tagged with satellite linked radio transmitters during the 11 years between 2001 and 2011 were analysed. With this time series, it is possible to investigate the effect of increasing temperature of preferred water mass temperature and temperature at depth where most bowhead feeding occurs through sea surface temperature (SST) on bowhead whale behaviour. We used daily positions and daily SST to develop seasonal Tweedie generalised linear mixed models to model the duration that bowhead whales spend in 20 x 20 km cells as a function of SST. The model was fitted on a much finer spatial and temporal scale than in previous studies, thus enabling a more detailed understanding of behaviour relative to water temperature. Our study demonstrates that bowhead whales spend more time in water with colder surface temperatures, suggesting that as waters continue to warm, bowheads may move further north, potentially reducing their overall available habitat.