Whales that refused to migrate for the winter heralded the destruction of the Arctic ecosystem


Whales that refused to migrate for the winter heralded the destruction of the Arctic ecosystem

Their singing recorded anomalous behavior of the bowhead whales population. Instead of the annual migration to the south, they remained in the Arctic Ocean and even demonstrated their mating rituals.

This unusual phenomenon involves significant shifts in the entire aquatic ecosystem of the Arctic, which is most likely the fault of global warming. Scientists will debate the causes of the unprecedented anomaly for a long time to come, and more data will be needed to find the most reliable answers. But the information already available to Canadian marine biologists tells us something else: the ecosystem of the Arctic Ocean is undergoing profound changes. And the consequences could be catastrophic.

According to a recent publication in a peer-reviewed scientific journal of the Royal Society of London, a significant part of the bowhead (or polar) whale population was left to overwinter in Amundsen Bay. Usually, in early autumn, about 20,000 giant animals migrate from the Beaufort Sea through the Chukchi Sea to the Bering Sea. In the north of the Pacific Ocean, the winter, and when the water gets warmer, they repeat the journey of more than six thousand kilometers in the opposite direction.
But in the winter of 2018-2019, something went wrong – and scientists began receiving reports of sightings of bowhead whales in Amundsen Bay. The coastal waters of Canada are home to colossal marine animals during the summer, so the anomaly was rushed to be studied immediately. In the history of observations, such a thing had never happened.

At the University of Capilano, Victoria, British Columbia, employees turned to a network of underwater acoustic sensors located in Arctic waters. Using special software, they found that between October 2018 and April 2019, between 0.5 percent and 3 percent of recordings contained evidence of giant mammals. These observation stations are in four locations where bowhead whales are only seen in the summer.
Most surprisingly, singing can be heard on several recordings – a behavior scientists associate with the mating rituals of these animals. Typically, the search for a mate and the mating process in bowhead whales occurs in spring or early summer, when they are still traveling in the off-season. In other words, something in the calendar of the most significant inhabitants of local waters has seriously changed.

Among the possible causes of this anomaly, marine biologists put global warming in the first place. All other reasons not to migrate may influence only indirectly or be a direct consequence of climate change. It is known that bowhead whales are susceptible to water temperature: a narrow range between minus 0,5 and two degrees Celsius is comfortable for them. As the environment warms, the animals begin to experience literal overheating and tend to migrate northward.
Decreasing ice cover could be a reason to cancel the annual migration. But in the winter of 2015-2016, when there was the least ice in the last half-century, no such anomaly was observed. And whales don’t care about ice: there were recorded cases when strong individuals of this species quickly broke through a cover about 20 centimeters thick. The sea giant wanted to eat and hunt for plankton, where it found food, even though there was a small obstacle on top. And thicker ice rarely forms in the habitat of bowhead whales.

Avoiding predators and protecting resources is another possibility. Due to climate change, the food base in the Beaufort Sea in winter probably did not decrease as much compared to summer. As a result, whales remained in Amundsen Bay, making it a food-rich place for possible competitors.
And from killer whales is easier to defend in familiar waters. Moreover, the long journey involves the risk of seeing these vicious predators sail farther south.

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