Ecology and Physiology of Narwhals
Narwhals in a summer ground
Narwhals are gregarious Odontocete whales, and are the most specialised of all Arctic Cetaceans [2]. Unique features of Narwhals that define them from other cetaceans include their horn-like tusk, attraction to ice covered areas and the ability to dive to astonishing depths [2]. They occur year-round in the high Arctic or subarctic areas of the North Atlantic at latitudes of above 60oN, and are narrowly distributed around Greenland, Baffin Island, the Canadian High Arctic Archipelago, Hudson Bay and the Hudson Straight [2;6;7]. A high proportion of individuals are found in Baffin Bay [1;3].
Narwhals utilise separate summer and winter grounds based on the distribution of pack ice or fast ice [3; 7]. They migrate north in summer to areas that are inaccessible during winter [3]. Migration occurs across a 2 month period [3]. Summer grounds consist of ice free shallow bays, whilst winter grounds are more offshore and require a substantial amount of ice cover with limited open water [6]. In winter grounds they are often found in deep water searching for prey such as Greenland halibut and squid [6]. Narwhals are highly dependent on predictable seasonal change in sea ice, and are therefore more vulnerable to the effects of climate change in the Arctic [2; 3; 6].
Narwhals utilise separate summer and winter grounds based on the distribution of pack ice or fast ice [3; 7]. They migrate north in summer to areas that are inaccessible during winter [3]. Migration occurs across a 2 month period [3]. Summer grounds consist of ice free shallow bays, whilst winter grounds are more offshore and require a substantial amount of ice cover with limited open water [6]. In winter grounds they are often found in deep water searching for prey such as Greenland halibut and squid [6]. Narwhals are highly dependent on predictable seasonal change in sea ice, and are therefore more vulnerable to the effects of climate change in the Arctic [2; 3; 6].
|
High fidelity to certain sites used during the different season is seen within narwhal populations [2;3]. This means that narwhals return to the same region in the higher latitudes every summer, and migrate south to the same sites every winter. The majority of energy intake for narwhals occurs over winter, where benthic feeding behaviours are adopted. Less intense feeding activities are seen during summer [6].
|
Narwhals are air breathers and cannot maintain or create open breathing holes in thick ice; therefore they require cracks and leads in the pack ice to be able to breathe [1;2;3;9]. The position and abundance of these cracks and leads determine where narwhals are able to persist, creating a considerable environmental challenge for the animals [1;2;3]. Narwhals are able to remain submerged for between 21 and 26 minutes, diving to maximum depths of approximately 990m [9].
The International Union for Conservation of Nature (IUCN) has listed narwhals as “near threatened” due to their high sensitivity to climate change [7]. Factors influencing this sensitivity include a “narrow geographic distribution, specialized feeding and habitat choice, and high site fidelity” [4]. The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) have also listed narwhals as being of “special concern”, requiring immediate conservation [7].
Narwhals arose during the Pliocene, and it is evident that they adapted to and survived periods of great environmental change [3]. Whilst this may be true, these changes occurred over a much longer time scale than the changes we observe today [3]. Therefore, narwhals may not be capable of coping with rapid alterations to pack ice, habitat and prey availability due to anthropogenic induced climate change, and are subject to extinction.
The International Union for Conservation of Nature (IUCN) has listed narwhals as “near threatened” due to their high sensitivity to climate change [7]. Factors influencing this sensitivity include a “narrow geographic distribution, specialized feeding and habitat choice, and high site fidelity” [4]. The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) have also listed narwhals as being of “special concern”, requiring immediate conservation [7].
Narwhals arose during the Pliocene, and it is evident that they adapted to and survived periods of great environmental change [3]. Whilst this may be true, these changes occurred over a much longer time scale than the changes we observe today [3]. Therefore, narwhals may not be capable of coping with rapid alterations to pack ice, habitat and prey availability due to anthropogenic induced climate change, and are subject to extinction.