A narwhal emerges for a breath in a lead, or crack, in the pack ice. NOAA Image courtesy of Mads Peter Heide-Jørgensen.
Narwhals may be creatures of habit, but they are also survivors. They are able to live in one of the most extreme environments on the planet. Since they evolved thousands of years ago, this environment has undergone large fluctuations in climate, including several glacial periods.
It’s this duality in the narwhals’ personality that makes it challenging to know how they would react to a new regime of change—possibly unlike any they’ve ever experienced in their natural habitat.
“That’s the real question,” Laidre says. “What’s stronger: the narwhals’ innate behavioral patterns or their instincts to adapt to a changing climate?”
In the case of the recent entrapment events, if seasonal sea ice expansion and retreat patterns shift, will it change the narwhals’ migratory timing? That’s the question that Harry Stern, a sea ice expert and colleague of Laidre’s at the University of Washington’s Polar Science Center, could help her answer.
Stern used satellite observations to examine sea ice patterns in the six largest narwhal summering grounds over a period of 31 years. He noticed that the annual sea ice freeze-up that takes place during the fall has been occurring progressively later with each passing year. In recent years, the autumn freeze-up has occurred roughly 3-4 weeks later than it did in the 1980s.
This trend is a symptom of a rapidly warming Arctic region—the gradual loss in sea ice observed over the last few decades allows the water to stay open longer and absorb more heat, which prolongs the melting season.
Because the narwhals’ summering areas are remaining open for longer, one possible theory is that the whales are lingering there, delaying their migration south until later in the fall and winter.
“Suddenly a very cold event—a large drop in temperature or a shift in the wind—will freeze up a smaller area very rapidly and trap the whales,” Laidre says. “Meanwhile, because they’ve delayed their return, the larger area around them has already frozen over. So there are not many alternatives in terms of places to go once they’re trapped.”
Laidre requires more data to further investigate this entrapment theory and determine whether the narwhals actually changed their usual behaviors and lingered longer due to the delayed sea ice freeze-up, or whether these are just random events. But she feels she can conclusively and confidently say that both the narwhals’ summering areas and wintering areas are changing.
Laidre expects to see some response to these changes, either in the animals’ behavior or population levels. Even if the narwhals themselves are not directly affected, their food sources could be.
“It’s a pretty good evolutionary strategy: the narwhals do the vast majority of their foraging at their wintering grounds where their food source is predictable,” Laidre says. “But the system is changing, and if the Greenland halibut suddenly are at lower densities or the food source isn’t as predictable any more, that’s a concern. Suddenly the narwhals’ strategy for survival isn’t so great.”
There is no evidence that this is happening yet. That’s the future direction of Laidre’s research: teasing out the links between changing Arctic conditions and narwhal behavior, and establishing a baseline of data so that she can identify any changes that develop in the future.
The rest of us may want to keep an eye on her progress. Just as the narwhal has appeared in legends and tales throughout history, it may inspire a new story about the whale’s success in navigating the impacts of climate change—or a cautionary tale about the heavy costs that come with it.
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Laidre K.L., M. P. Heide-Jørgensen, H. Stern, P. Richard. 2012. Unusual narwhal sea ice entrapments and delayed autumn freeze-up trends. Polar Biology 35: 149-154. DOI 10.1007/s00300-011-1036-8
Laidre, K. L., M. P. Heide-Jørgensen, W. Ermold, and M. Steele. 2010. Narwhals document continued warming of southern Baffin Bay. Journal of Geophysical Research 115: C10049, doi:10.1029/2009JC005820.
Laidre K.L. and M.P. Heide-Jørgensen. 2011. Life in the lead: Extreme densities of narwhals in the offshore pack ice. Marine Ecology Progress Series 423:269-278.
Tracking Narwhals in Greenland. NOAA Ocean Explorer.