One concern of changing sea ice cover is that loss of sea ice, particularly during the summer, may increase the access of killer whales to narwhals, thus increasing predation. Access to narwhals by man is also changing with changes in sea ice concentration and extent. In Smith Sound, climate change may have decreased spring and summer ice cover, which has enabled people in north Greenland to access the area and increase their catches (Nielsen 2009). The presence of open water is an important influence on the narwhal hunt, with the majority (72%) of the hunt in Nunavut taking place during the summer months (July 25th–October 1) (White 2012). Narwhals have also recently been moving further west in the Canadian Arctic, perhaps due to changes in sea ice cover, and been sighted and hunted near communities in the Central Canadian Arctic where they have been seldom seen before (White 2012).
Increasing industrial development in the Arctic, especially increased ship traffic, could also pose a threat to narwhal populations. Narwhals can detect the noise made by large icebreakers from at least 25 to 30 km away (Cosens and Dueck 1993). Other studies have found narwhals reacting to such noise at distances from 40–60 km (Finlay et al. 1990, Cosens and Dueck 1988). Communities close to shipping routes in the NW Passage, Arctic Bay and Pond Inlet, report fewer narwhals in their areas than there has been in the past, and some hunters attribute this to increased ship traffic (White 2012). This is a concern as ship traffic is expected to increase as sea ice cover decreases with global warming.
Prior to 1996, there had been very little fishing in NAFO Division 0A, the waters on the Canadian side of Baffin Bay. Since 1998, the Greenland halibut fishery in this area has expanded. Currently, both otter trawls and gillnets are used in this fishery. As the fishery expanded, concerns were raised by both DFO and the Nunavut Wildlife Management Board that narwhals could be affected by removal of their primary prey species on their overwintering grounds, damage to bottom habitat by trawling, and entanglement of whales in lost gillnets.
In order to mitigate these concerns, a number of measures were introduced. For example, an end date of Nov. 10 was established for the gill net season, in an effort to reduce the risk of gear loss due to late season ice conditions. This date may be changed in response to seasonal conditions. As well, starting in 2007, the southeast part of NAFO area 0A was closed to Greenland halibut fishing in order to protect this important food source for overwintering narwhals.
Photo: J. Blair Dunn
Better drilling technology and a warming climate have increased interest in northern areas previously inaccessible to oil and gas exploration. It has been estimated that more than 20 million barrels of undiscovered oil and still greater quantities of natural gas might exist on the continental shelf of East and West Greenland, with still more in the Canadian Arctic Archipelago (Gautier et al. 2009). Seismic exploration, which involves the discharge of airguns that create very loud low-frequency sounds underwater, have been conducted off West Greenland since 2007, and is expected to begin soon off East Greenland. Recently, Heide Jørgensen et al. (2013c) reviewed the potential effects of these activities on narwhals and other Arctic marine mammals.
Like all toothed whales, narwhals use their echolocation abilities to find prey, avoid predators and in navigation. Narwhals also use it to find openings in dense pack ice where they can come up to breathe. In addition to echolocation, narwhals have a broad vocal repertoire which they use to stay in touch with other members of their pod. Their Arctic habitat has heretofore been largely unaffected by human-caused sounds, to which they are therefore unaccustomed.
The effects of ship noise, seismic exploration, drilling and other sounds on narwhals have been largely unstudied, but could include short or long term changes in behaviour, such as feeding activities and vocalization. Noise could also induce avoidance responses and changes in migratory timing and routes. Extremely loud sounds, such as those produced by seismic exploration, have the potential to directly damage narwhal hearing if they occur at close range, in addition to masking environmental sounds that may be important to narwhals. Narwhals have been observed to react to vessel noise even at long distance and low sound intensity, generally by leaving the area and reducing their vocalizations.
Narwhals spend about half the year in their winter feeding areas, in a marine environment covered by dense pack ice. Although narwhals are among the most ice-adapted of whales, they are still subject to occasional entrapments when the ice freezes up or closes around them, leaving them dependent on a small breathing hole and often resulting in their death when the breathing hole closes. The circumstances leading to entrapments are well known to the Inuit inhabitants of Disko Bay in West Greenland, who historically have harvested whales that have become entrapped. However, in recent years, entrapments have occurred in other areas where they have not been frequently observed, leading Heide-Jørgensen et al. (2013c) to speculate that seismic activities in Baffin Bay may have contributed to these events.
In November 2008, over 1,000 narwhals were entrapped in the ice near Pond Inlet, Nunavut, in an area of Lancaster Sound that freezes solid in the winter and is not therefore winter habitat for cetaceans. Previous tagging experiments have demonstrated that most narwhals begin their southward migration from this area by the end of September. However, seismic exploration was occurring in Baffin Bay in September and October of the same year, and it is possible that the noise produced by this activity may have delayed or prevented the narwhals from migrating, and contributed directly to the entrapment. All of these animals eventually died, most of them harvested by local Inuit who knew they would not survive the winter.
Smaller entrapments occurred in Inglefield Bredning in Northwest Greenland in November 2009 and February 2010. Again, this is normally summer habitat for narwhals and they are thought to leave the area well before November. And again, seismic activity in Baffin Bay in September and October 2009 may have delayed or prevented their migration from the area.
While these occurrences do not constitute conclusive proof that seismic activities are affecting the timing of narwhal migrations, they certainly demonstrate the need for caution in pursuing these activities in or close to narwhal habitat. Heide-Jørgense et al. (2013c) conclude that further research on the effects of anthropogenic noise on narwhals and other Arctic marine mammals is urgently needed, and that this research should ideally precede any further such activities in the area.
|Watch a video of narwhals swimming into ice and becoming temporarily entrapped|