(EarthSky.org)
Fear of killer whales makes sea creatures run, dive or hide
New research suggests that, as climate warms and killer whales find new hunting grounds, marine ecosystems will be affected.
New research has combined scientific observations with Canadian Inuit traditional knowledge to how killer whales (Orcinus orca) in the Arctic eat and behave. Researchers from Manitoba visited 11 Canadian Nunavut Inuit communities and collated information from over 100 interviews with hunters and elders as part of this research. They published their results on January 29, 2012 in the open access journal Aquatic Biosystems, saying that the increase in hunting territories available to killer whales in the Arctic due to climate change and melting sea ice could "seriously affect the marine ecosystem balance."
Transient killer whales near Unimak Island, eastern Aleutian Islands, Alaska. They are top predators that affect the behavior of their prey, causing them to run away, dive deep or try to hide among sea ice. Image Credit: Wikimedia Commons
Killer whales are top marine predators wherever they are found. According to these researchers, the whales "seem to eat everything from schools of small fish to large baleen whales, over twice their own size." "Aarlirijuk," or the fear of killer whales, apparently influences the behavior of killer whales' prey. Smaller mammals seek refuge in shallow waters or on shore, and larger prey run away, dive deep, or attempt to hide among the ice. Even narwhal, which are capable of stabbing a killer whale with their tusks (although this is likely to result in the deaths of both animals), will run to shallow waters and wait until the whales give up.
The type of reported prey varied between areas. Most incidences of killer whales eating bowhead whales occurred in the Arctic's Foxe Basin, while narwhal predation was more frequent around Baffin Island.
Inuit were also able to describe first-hand how killer whales hunted, including several reports of how killer whales co-operated to kill the much larger bowhead. During the hunt some whales were seen holding the bowhead's flippers or tail, others covering its blowhole, and others biting or ramming to cause internal damage. Occasionally dead bowheads, with bite marks and internal injuries but with very little eaten, are found by locals.
Even narwhal, which are capable of stabbing a killer whale with their tusks (although this is likely to result in the deaths of both animals), will run to shallow waters and wait until the whales give up. Image Credit: Wikimedia Commons
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In this research, the Inuit who were consulted about the diets of killer whales reported that killer whales would `eat whatever they can catch', mainly other marine mammals including seals (ringed, harp, bearded, and hooded) and whales (narwhal, beluga and bowhead).
However there was no indication that Arctic killer whales ate fish. Only seven of the interviewees suggested that killer whales ate fish, but none of them had ever seen it themselves.
Killer whales have recently started colonizing Hudson Bay (possibly due to loss of summer sea ice with global warming). Local communities are reliant on the very species that the orcas like to eat. Dr Steven Ferguson from the University of Manitoba who led this research commented, "Utilizing local knowledge through TEK will help scientists understand the effects of global warming and loss of sea ice on Arctic species and improve collaborative conservation efforts in conjunction with local communities."
Bottom line: Killer whales in the Arctic, which are top predators, eat a variety of foods and influence the behavior of their prey, according to a new study led by Dr. Steven Ferguson from the University of Manitoba, published January 29, 2012 in the open access journal Aquatic Biosystems. If, as scientists expect, climate continues to warm, the whales will affect marine ecosystems different from those they now inhabit. For example, the whales have started colonizing Hudson Bay in recent years, where local communities are dependent on the species orcas like to eat.
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