Bad news for ice-reliant species, as global climate change decreases seasonal sea ice coverage in the Arctic. It is reported that over the last 30 years in the Chukchi Sea, which is located just north of the Bearing Strait between Russia and Alaska, there has been a shift to earlier spring melts and later fall freezes of Arctic sea ice. With this increase of open water days in the North by 5-6 weeks, it is all good news for some subarctic species such as the killer whales.
Killer whales produce echolocation whistles, clicks, and pulsed calls, for communication and navigation. So, back in 2009 researchers began using underwater acoustic monitoring to detect killer whales within the Chukchi Sea. From these, the recordings of killer whale calls occurred as early as June 1st and as late as November 16th confirming these shifts to longer residency during the cooler months.
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Now these killer whales aren’t necessarily new to the area however, they are usually only seen for a few weeks during the warmest months of the year. This is because throughout the cold months killer whales have difficulty migrating North of the Bearing Strait as it is normally iced over and instead, spend most of their time a little further South. However, this is not the case anymore and is particularly concerning for many local marine mammals who aren’t used to killer whales being more North during this time of year and sticking around for so long.
The affects of killer whales on local marine mammals has already begun and is evident not only in the Chukchi Sea but the Hudson Bay as well. This increase in sightings of killer whales in the Hudson Bay is also very much correlated to the increase in sea ice melts along “choke points” where multiyear sea ice previously restricted migration into this area. Some of the affected mammals in the Hudson Bay and Chukchi Sea include walruses, narwhals and beluga whales. In Narwhals particularly, there is evidence that their normal behaviour is shifted when in the presence of the killer whale. There have also been more occurrences of killer whale rake markings on the flukes of bowhead whales indicating their interaction. The evidence for such disruption suggests that in these areas, the presence of killer whales is causing ecological shifts in the predator-prey trophic relations. This is strongly due to the fact that killer whales are an apex predator, meaning they have no predators themselves and therefore, they can roam freely.
As our Earth continues to warm and “choke points” such as the Bearing Strait continue to reduce in multiyear sea ice, we should continue to see walrus, narwhal, and beluga whale populations diminish, in the Hudson Bay and the Chukchi Sea. It is likely that studies will continue to show that killer whales, as well as many other marine mammals will expand further into the Arctic in the near future and who is to know what this will affect next.
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