Impacts of climate warming, declining sea ice on Arctic whale migration

Date: November 16, 2016

Source: Florida Atlantic University

Declines in the Arctic sea ice are arguably the most dramatic evidence of the effects of current climate warming on ocean systems. Native peoples of the far north have long appreciated and relied upon the migrations of animals with the changing seasons, including some of the largest and least studied, the Arctic whales. While sea ice is perhaps the most defining feature of their habitat, the relationship between Arctic whales and sea ice is still largely a mystery, and there is increasing concern over how these species will adapt to climate related changes in sea ice.

Researchers from Florida Atlantic University's Harbor Branch Oceanographic Institute and a team of scientists working in collaboration with Native hunters in Alaska and Canada have just published results of a study in the Royal Society Biology Letters titled, "Genetic Profiling Links Changing Sea Ice to Shifting Beluga Whale Migration Patterns," assessing the relationship between changing sea ice and beluga whale migration as well as summer residency patterns of a number of populations over two decades of dramatic sea ice changes in the Pacific Arctic. The researchers found that beluga whales, often known as the white whale, (Delphinapterus leucas) exhibited a tremendous ability to deal with widely varying sea ice conditions from one year to the next over a 20-year time frame in their return to traditional summering grounds each year.

"It was not clear how sea ice influences beluga whale migration patterns and their summer habitat use, and climate change has added urgency to determining how environmental factors might shape the behavior and ecology of this species," said Greg O'Corry-Crowe, Ph.D., lead author and a research professor at FAU Harbor Branch, whose research focuses on combining molecular genetic analysis with field ecology to study the molecular and behavioral ecology of marine apex predators.

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Migrating whales provide entertainment for dolphins - Photo

September 2013. In the photo, a group of long-beaked common dolphins are hitching a free ride on the bow wave of a migrating gray whale. Taken near Catalina Island off the coast of Southern California, the photo was shot from about 600 feet by scientists with the Cetacean Health and Life History Program at the US National Oceanic and Atmospheric Administration's (NOAA) Southwest Fisheries Science Center.

Migration

Every year, almost the entire population of eastern North Pacific gray whales migrates from their feeding grounds in the Arctic down to their breeding and calving grounds off the coast of Baja California, Mexico. And most years, NOAA scientists survey and photograph the whales from the air. By analysing the high-resolution photos, scientists can tell how well-nourished the animals are, how many females are pregnant, and how many new calves are born.

Health check

One reason for doing this is to keep an eye on the health of the gray whale population. But in addition to that, the photographic study is an indirect way of monitoring the Arctic ecosystem. The primary feeding grounds for the eastern north Pacific population of gray whales are in the Arctic. The rest of the year they fast or eat very little. So their physical condition during migration reflects conditions in their feeding grounds in the Arctic.

Climate change

"We know the Arctic is changing, and changing pretty rapidly," said Wayne Perryman, a biologist with NOAA's Cetacean Health and Life History Program. "We want to know how this is impacting the gray whale population."

For example, many of the species that gray whales feed on are shifting northward as the Arctic warms. This means that gray whales have to migrate further north to feed. For pregnant females, who by the time they arrive in the Arctic have been fasting for many months, this extra travel may be energetically taxing. One of the things that Perryman and his colleagues are studying is the relationship between the length of the migration and the rate of successful pregnancies.

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