|Orcinus orca. Uploaded by EvaK. CC 2.5 Senckenberg Museium Frankfurt Germany
Compared to the three most notable Arctic whales (bowhead, beluga, and narwhal) the killer whale is at a bit of a disadvantage in ice- it has a huge dorsal fin, especially among the males where it might be 2 meters tall. So although they do move up to the edge of the pack ice in the Arctic and Antarctic they do not penetrate very far into the pack ice or areas with large amount of floating ice due to obviously painful scrapings and cuts that constant abrasion against ice would incur. So not only is ice a hunting platform for polar bears and a resting/birthing stations for seals - it a sanctuary of sorts for Arctic whales from killer whales. But a spate of incidents suggests that the sanctuary that ice provided whales in the high Arctic Canadian archipelago and Hudson Bay is no more. There is a bloodbath in paradise.
|Glenn Williams. Narwhals jousting
"We saw this big bloodstain in the water", and "You could smell the blubber in the air. And the killer whales were moving onto the next one, like nothing had happened." so describes a witness to an increasingly familiar but previously rare event - killer whales moving into Hudson Bay and targeting beluga whales in the estuaries and bays that they traditionally stayed in during the summer months in relative safety. Orcas Pop Up near Churchill, Feed on Beluga. What was at most an ephemeral and rare predatory encounter between the two species is looking more and more like a deliberate hunt by the killer whales. The ice disappears earlier and arrives later allowing the orcas to move in and stay longer. There has been the suggestion that some recovering populations are being suppressed and others may be further diminished. Sometimes the killer do not make it out of the Bay in time, as occurred last year when a pod was trapped - but eventually freed by currents.
|photo credit Davidee Mina. killer whales trapped Hudson Bay
Invasion of the Killer Whales. Nature PBS December 18, 2014.
The portrait painted by the above highly recommended Nature documentary is one of an ecosystem in flux. Polar bears scrounging for carcasses on the beach, sea bird eggs, and fishing for Arctic char in rivers. And killer whales moving into an ecosystem in which they had previously been kept at bay. Moving with a purpose, covering over 200 km a day to seek out narwhal populations in the Canadian Archipelago from which they could not reach before. Bowhead whales evincing massive scars and bites from killer whales and switching their movements towards areas that retain ice year round to avoid the killer whales. Playing a game of cat and mouse the two whales listen to eachother across vast expanses of ocean.
|Tagged killer whales (red) versus tagged Bowhead whales (yellow) showing avoidance patterns
|Bowhead fluke w/killer whale maulings
"I was hunting these narwhals and they were fleeing from some killer whales. The killer whales were travelling fast and upside down. And they breached the water chasing the narwhal. When they got close to the shore where the narwhal were they took bites out of two of them very quickly. This is when I realized that they are supreme hunters." Inuit elder.
"We knew changes were happening and wanted to understand them... We anticipated a change from the bottom up... We recognized the killer whale as that top predator that was all of a sudden making these huge changes in the Canadian Arctic. And it was something we didn't really think about at the start but there it was staring us in the face." Steve Ferguson, Canadian fisheries biologist on realizing that simultaneous with a bottom up trophic cascade in the Arctic a top down trophic pressure via killer whales was also occurring.
While killer whales in the eastern Canadian Arctic appear to be expanding their range to include areas westward and northward and capitalizing on prey/feeding grounds previously out of their reach between Alaska and Siberia on a group of islands called the Diomedes they have been documented predating on walrus recently. The following clip I scrounged up on Youtube is to the best of my knowledge the first video documentation of such an occurrence.
Walrus, which are themselves recognized as keystone species due to the significant bioturbation they do when digging up benthic prey and are significant in the diet of Inuit, are also highly dependent on ice for resting upon. Loss of ice concentrates walrus in large herds on the land which might further enable killer whales to find and target these large seals.
Polar bears have also been documented targeting these concentrations of walruses, although concentrating usually on the young. Another food source grounded polar bears have been utilizing during the summer months are runs of a type of arctic salmon called arctic char.
|Polar Bears hunting Arctic Char. Nature
Global ecosystem change is already afoot. Some will adapt. Some will move. Some will benefit. And some will perish. How this will all play out and what surprises await who can say?
|(c)US Navy. public domain. USS Honolulu 450 km (280 mi) from N. Pole
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