We know that as the sea ice shrinks, animals that depend on it for survival will struggle. But we know a lot less about what will happen to the myriad of species that rely on it indirectly. One such creature is the beluga whale, and a new study has revealed that their behavior is already changing as a result of the loss of sea ice.
“I think this paper is novel in that we're presenting some of the first indirect effects of sea ice loss for an Arctic whale species,” said Donna Hauser, who led the study published in Diversity and Distributions. “As changes in sea ice affect oceanographic properties, that could be affecting the distribution, abundance or species composition of prey for belugas.”
Belugas are found throughout the Arctic Ocean, and many populations migrate with the shifting sea ice. As the ocean starts to freeze, the whales move south toward open water where they feed at depth alongside the pack ice, and even underneath the sea ice at times. When summer kicks in and the ice begins to melt, the belugas then return north and spend the warmer months in estuaries and the mouths of rivers.
The team of researchers used two sets of data on the group of whales that make an annual migration from their wintering grounds in the Bering Sea to their summer pastures in the Chukchi Sea, off the north coast of Alaska. The first set, which they termed the “early” data, was collected between 1993 and 2002, while the “late” set was recorded between 2004 and 2012.
This data included not only where the belugas were going, but also details on how deep they were diving for and for how long. This was then compared to how the extent of sea ice has fluctuated over the same period, and the researchers noticed a pattern.
The extent of the sea ice seemed to have an impact on the foraging behavior of the beluga whales. As the extent of the sea ice shrunk during the “late” period, the whales were diving for significantly longer and deeper. While during the early period, the whales would dive maybe once a day for 20 minutes to a depth of roughly 50 meters (164 feet), by the later period they were diving close to three times a day down to around 64 meters (210 feet).
This change in foraging behavior is likely to reflect a change in the distribution of their food, which includes a variety of prey from salmon and cod to crabs and squid. The researchers suspect that as the ice is melting, it is influencing the ocean currents and in turn altering where the food is found.
Whether or not this is a good or bad thing for the whales is hard to discern. The whale populations are stable, and the improved foraging could be a benefit to them. On the other hand, the increase in diving could be imposing new costly energetics on the animals.
1