Pagophily

Last updated
The polar bear is an example of a pagophilic species. Polar Bear AdF.jpg
The polar bear is an example of a pagophilic species.

Pagophily or pagophilia is the preference or dependence on water ice for some or all activities and functions. The term Pagophila is derived from the Ancient Greek pagos meaning "sea-ice", and philos meaning "-loving".

Contents

Pagophilic animals, plants, etc. prefer to live in ice or perform certain activities in the ice. For example, a number of ice seals are described as pagophilic as they have adapted to breed and feed in association with their ice habitat. The preference for a frozen habitat has been observed in several mammalian, avian and invertebrate species.

Evolutionary and adaptive basis

The dependence and preference for ice and snow is believed to have an evolutionary basis dating back to the last ice age, approximately 2.6 million years ago. In a period where the earth was covered in ice pans, the ancestors of pagophilic mammals developed the ability to hunt on and around ice out of necessity. Some researchers have argued that life originated in icy habitats, in the form of microorganisms that can survive in harsh conditions. Furthermore, the study of pagophilic organisms on earth has contributed to the belief that life is present on other extremely cold planets. [1] Survival in extreme habitats such as ice habitats is possible due to behavioural and/ or physiological adaptations. These adaptations may include: hibernation, insulation in the form of fat or blubber, increased hair or feather growth, or the presence of an antifreeze-like enzyme. [2] [3]

Pagophily is beneficial for survival, and often critical. Pagophilic mammals can use ice as a platform to get closer to prey, or to get farther away from predators. Sea ice can also be used for breeding, nurturing young and other behaviours if there is less risk for predation on the ice than on land. For many animals their primary food supply may live near the ice as well or in the water under the ice.

In mammals

Phocidae

The family Phocidae is a family of pinnipeds, known as "true seals". A study by Stirling (1983) indicated that the formation of large amounts of ice on coastlines approximately 15 million to 5 million years ago forced many early phocine seals to adapt their breeding and feeding behaviour due to their ice habitats. [4] According to the National Oceanic and Atmospheric Administration ice seals are found in the Arctic and Antarctic. [5] Breeding behaviour, specifically, the nursing of pups has been researched extensively in ice-living seals. The evolution of feeding behaviours and diets of ice-dwelling seals in both the Arctic and the Antarctic has also been studied.

Ice-breeding and lactation periods

Weaned seal pup Weaned harp seal pup.jpg
Weaned seal pup

Among phocid seals, there is some variation of how maternal and pup behaviour takes place during lactation. Variation is dependent on access to the water, risk of predation and access to food. There are two main strategies seen in seal breeding in ice habitats. The first strategy is observed in grey seals, hooded seals and harp seals. These animals display a short lactation period in which a large amount of energy is transferred from the mother to the pup. Pups are inactive during this time and have not yet entered the water. In bearded seals, less energy is transferred to pups over a longer period of time, pups enter the water and begin feeding independently while they are still receiving milk from their mother. [6]

Researchers argue that there is an adaptive basis of both behaviours. In a longer lactation period where relatively low amounts of energy are transferred to pups over a long period of time, pups stay closer to their mothers and are protected from predators. In a shorter lactation period, pups are weaned at a young age and as a result, become independent in feeding. In addition to early independence, milk given to pups during this brief period has a very high energy content. [7]

The evolution of brief lactation periods and high energy transfer is related to the habitat of the seals. Species that give birth to their pups on stable substrate, such as land or "fast-ice" (which is attached to land) have longer lactation periods and take longer to achieve feeding independence. Species that give birth on unstable ice pans have short and efficient lactation periods so that their young can achieve independence and develop adequate fat/blubber layers before the ice melts or moves. [7] The development of short lactation periods in most phocid seals is an adaptation that has allowed them to succeed and thrive on ice. Pups receive high amounts of fat during their short lactation period and thus achieve independence at a young age.

Ice-feeding

Research on ringed seals in the Arctic has shown that young seals mainly consume invertebrates while adult seals consume primarily Arctic cod. The dietary differences between younger and older ice-seals is likely due to differences in diving capabilities and foraging experience. The capture of invertebrates is easier for juvenile seals due to their lack of hunting experience. Adult ice-seals, however, prefer to consume fish due to their high energy content. [8]

Diving behaviour is critical for hunting in adult seals. [8] Seals pursue their prey, primarily fish, by diving under fast-ice. The ability to dive underneath the ice is important for catching prey. Research by Davis et al. has highlighted the importance of seals' vision. When diving deep below the ice, limited light poses a challenge to hunting. [9] The adaptation of amphibious seal vision has contributed to the evolution of pagophilia in seals. [9] [10]

Polar bear

Polar bear with its prey. Polar bear (Ursus maritimus) with its prey.jpg
Polar bear with its prey.

The polar bear (Ursus maritimus) is dependent on sea ice for hunting and feeding. Seals are the primary food source for polar bears so the amount of time that they spend living on ice is largely dependent on ice-seal populations. Research by Mauritzen et al. has indicated that polar bear habitat selection (i.e. ice versus land) is determined by finding a balance between the benefits of abundance of prey on ice and the additional energy expenditure in ice habitats. Furthermore, polar bears that live on dynamic, constantly changing "open ice" have more access to prey than those that live on fast ice. [11]

U. maritimus possess a number of adaptations to allow them to survive in harsh, cold environments. These thermoregulatory adaptations that allow for the pagophilic lifestyle of the bears include a thick layer of fur, a thick hide and a layer of fat, also called blubber. [12]

In birds

Several species of marine birds live on ice caps in both the Arctic and Antarctic. [13] G.L. Hunt of the University of California has researched the adaptive basis for marine birds dwelling in "ice-influenced environments". According his research, sea ice can both inhibit access to foraging opportunities and provide enhanced experiences for foraging. In both the Arctic and Antarctic oceans, large populations of zooplankton, algae and small fish live directly under sea ice. Access to enhanced foraging opportunities is a plausible explanation for pagophily in marine birds. [13]

Genus Pagophila

Genus Pagophila is a genus of birds that consists of only one species: Pagophila eburnea, also known as the ivory gull. The ivory gull is found in the Arctic in the northernmost parts of Europe and North America.

Ivory gulls feed on crustaceans, fish and rodents and are also considered opportunistic scavengers. The gulls often follow pagophilic mammals such as seals and polar bears and feed on the remains of their prey.

In invertebrates

Edwardsiella andrillae Edwardsiella andrillae by ROV SCINI retraitee FL.png
Edwardsiella andrillae

Sea ice invertebrates serve as important food sources for many Pagophilic vertebrate species. [14]

Gammarus wilkitzkii

Gammarus wilkitzkii is an amphipod species that lives below Arctic sea ice. This organism uses a relatively wide variety of food sources including detritus, sea algae and the remains of other crustaceans. As a result of its harsh under-ice habitat, Gammarus wilkitzkii has developed a broad range of sources for nutrients to compensate for temperature and spatial changes of the ice. [15]

Edwardsiella andrillae

Edwardsiella andrillae is a recently discovered "ice-loving" sea anemone that was discovered in Antarctica. The white anemones were observed by scientists of the Antarctic Geological Drilling Program (ANDRILL). The organisms live burrowed in the ice, upside down with their tentacles "protruding out into the frigid water". This is the first species of sea anemone that has been observed to live in ice rather than on the ocean floor. Research regarding the diet and lifestyle of Edwardsiella andrillae is ongoing. [16]

Impact of climate change

Starving polar bear Endangered arctic - starving polar bear.jpg
Starving polar bear

Climate change and the reduction of sea ice in polar regions has had significant impacts on organisms that prefer or depend on ice habitats. A "stochastic population projection" has shown that there will likely be drastic declines in the polar bear population by the end of the 21st century. Polar bears rely on seals and fish as their primary food source. While the bears can hunt land mammals such as caribou and fox, they can survive off of land prey for only approximately 6 months. Without the abundance of sea ice, polar bears cannot access seals and fish and, thus, can starve. [17] These projections were important in the decision to list the polar bear as a threatened species under the U.S. Endangered Species Act. [17]

In addition to threatening polar bear populations researchers also argue that seal populations will also be impacted by climate change. "The breeding-habitat loss in their traditional breeding areas [will impact] distributional changes and in all probability abundance reductions". [18] Seals use ice to nurture their young and teach them to hunt; however, with the reduction of ice due to climate change, seals cannot teach their young to hunt before their lactation period is over. [4] Climate change poses a significant threat to pagophilic animals. [17]

See also

Related Research Articles

<span class="mw-page-title-main">Earless seal</span> Family of mammals

The earless seals, phocids, or true seals are one of the three main groups of mammals within the seal lineage, Pinnipedia. All true seals are members of the family Phocidae. They are sometimes called crawling seals to distinguish them from the fur seals and sea lions of the family Otariidae. Seals live in the oceans of both hemispheres and, with the exception of the more tropical monk seals, are mostly confined to polar, subpolar, and temperate climates. The Baikal seal is the only species of exclusively freshwater seal.

<span class="mw-page-title-main">Fur seal</span> Subfamily of mammals

Fur seals are any of nine species of pinnipeds belonging to the subfamily Arctocephalinae in the family Otariidae. They are much more closely related to sea lions than true seals, and share with them external ears (pinnae), relatively long and muscular foreflippers, and the ability to walk on all fours. They are marked by their dense underfur, which made them a long-time object of commercial hunting. Eight species belong to the genus Arctocephalus and are found primarily in the Southern Hemisphere, while a ninth species also sometimes called fur seal, the Northern fur seal, belongs to a different genus and inhabits the North Pacific. The fur seals in Arctocephalus are more closely related to sea lions than they are to the Northern fur seal, but all three groups are more closely related to each other than they are to true seals.

<span class="mw-page-title-main">Polar bear</span> Species of bear native largely to the Arctic Circle

The polar bear is a large bear native to the Arctic and nearby areas. It is closely related to the brown bear, and the two species can interbreed. The polar bear is the largest extant species of bear and land carnivore, with adult males weighing 300–800 kg (660–1,760 lb). The species is sexually dimorphic, as adult females are much smaller. The polar bear is white- or yellowish-furred with black skin and a thick layer of fat. It is more slender than the brown bear, with a narrower skull, longer neck and lower shoulder hump. Its teeth are sharper and more adapted to cutting meat. The paws are large and allow the bear to walk on ice and paddle in the water.

<span class="mw-page-title-main">Narwhal</span> Medium-sized species of toothed whale

The narwhal, is a species of toothed whale. It is a member of the family Monodontidae, and the only species in the genus Monodon. An adult narwhal is typically 3.5 to 5.5 m in length and 800 to 1,600 kg in weight. The most prominent feature of the species is an adult male's long single tusk that can be up to 3 m (9.8 ft). Instead of a dorsal fin, it possesses a shallow dorsal ridge. It is a social animal, and may associate in groups of up to 20 members. Carl Linnaeus scientifically described the species in 1758 in his work Systema Naturae.

<span class="mw-page-title-main">Marine mammal</span> Mammals that rely on marine environments for feeding

Marine mammals are mammals that rely on marine (saltwater) ecosystems for their existence. They include animals such as cetaceans, pinnipeds, sirenians, sea otters and polar bears. They are an informal group, unified only by their reliance on marine environments for feeding and survival.

<span class="mw-page-title-main">Pinniped</span> Infraorder of mammals

Pinnipeds, commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semi-aquatic, mostly marine mammals. They comprise the extant families Odobenidae, Otariidae, and Phocidae, with 34 extant species and more than 50 extinct species described from fossils. While seals were historically thought to have descended from two ancestral lines, molecular evidence supports them as a monophyletic lineage. Pinnipeds belong to the suborder Caniformia of the order Carnivora; their closest living relatives are musteloids, having diverged about 50 million years ago.

<span class="mw-page-title-main">Ringed seal</span> Species of carnivore

The ringed seal is an earless seal inhabiting the Arctic and sub-Arctic regions. The ringed seal is a relatively small seal, rarely greater than 1.5 m in length, with a distinctive patterning of dark spots surrounded by light gray rings, hence its common name. It is the most abundant and wide-ranging ice seal in the Northern Hemisphere, ranging throughout the Arctic Ocean, into the Bering Sea and Okhotsk Sea as far south as the northern coast of Japan in the Pacific and throughout the North Atlantic coasts of Greenland and Scandinavia as far south as Newfoundland, and including two freshwater subspecies in northern Europe. Ringed seals are one of the primary prey of polar bears and killer whales, and have long been a component of the diet of indigenous people of the Arctic.

<span class="mw-page-title-main">Bearded seal</span> Species of Arctic dwelling marine mammal

The bearded seal, also called the square flipper seal, is a medium-sized pinniped that is found in and near to the Arctic Ocean. It gets its generic name from two Greek words that refer to its heavy jaw. The other part of its Linnaean name means bearded and refers to its most characteristic feature, the conspicuous and very abundant whiskers. When dry, these whiskers curl very elegantly, giving the bearded seal a "raffish" look.

<span class="mw-page-title-main">Leopard seal</span> Macropredatory species of Antarctic seal

The leopard seal, also referred to as the sea leopard, is the second largest species of seal in the Antarctic. Its only natural predator is the orca. It feeds on a wide range of prey including cephalopods, other pinnipeds, krill, fish, and birds, particularly penguins. It is the only species in the genus Hydrurga. Its closest relatives are the Ross seal, the crabeater seal and the Weddell seal, which together are known as the tribe of Lobodontini seals. The name hydrurga means "water worker" and leptonyx is the Greek for "thin-clawed".

<span class="mw-page-title-main">Northern elephant seal</span> Species of marine mammal

The northern elephant seal is one of two species of elephant seal. It is a member of the family Phocidae. Elephant seals derive their name from their great size and from the male's large proboscis, which is used in making extraordinarily loud roaring noises, especially during the mating competition. Sexual dimorphism in size is great. Correspondingly, the mating system is highly polygynous; a successful male is able to impregnate up to 50 females in one season.

<span class="mw-page-title-main">Harp seal</span> Species of mammal

The harp seal, also known as Saddleback Seal or Greenland Seal, is a species of earless seal, or true seal, native to the northernmost Atlantic Ocean and Arctic Ocean. Originally in the genus Phoca with a number of other species, it was reclassified into the monotypic genus Pagophilus in 1844. In Greek, its scientific name translates to "ice-lover from Greenland," and its taxonomic synonym, Phoca groenlandica translates to "Greenlandic seal." This is the only species in the genus Pagophilus.

<span class="mw-page-title-main">Antarctic fur seal</span> Species of carnivore

The Antarctic fur seal is one of eight seals in the genus Arctocephalus, and one of nine fur seals in the subfamily Arctocephalinae. Despite what its name suggests, the Antarctic fur seal is mostly distributed in Subantarctic islands and its scientific name is thought to have come from the German vessel SMS Gazelle, which was the first to collect specimens of this species from Kerguelen Islands.

<span class="mw-page-title-main">Subantarctic fur seal</span> Species of carnivore

The subantarctic fur seal is a species of arctocephaline found in the southern parts of the Indian, Pacific, and Atlantic Oceans. It was first described by Gray in 1872 from a specimen recovered in northern Australia—hence the inappropriate specific name tropicalis.

<span class="mw-page-title-main">Weddell seal</span> Species of mammal

The Weddell seal is a relatively large and abundant true seal with a circumpolar distribution surrounding Antarctica. The Weddell seal was discovered and named in the 1820s during expeditions led by British sealing captain James Weddell to the area of the Southern Ocean now known as the Weddell Sea. The life history of this species is well documented since it occupies fast ice environments close to the Antarctic continent and often adjacent to Antarctic bases. It is the only species in the genus Leptonychotes.

<span class="mw-page-title-main">Caspian seal</span> Species of seal endemic to the Caspian Sea

The Caspian seal is one of the smallest members of the earless seal family and unique in that it is found exclusively in the brackish Caspian Sea. It lives along the shorelines, but also on the many rocky islands and floating blocks of ice that dot the Caspian Sea. In winter and cooler parts of the spring and autumn season, it populates the northern Caspian coastline. As the ice melts in the summer and warmer parts of the spring and autumn season, it also occurs in the deltas of the Volga and Ural Rivers, as well as the southern latitudes of the Caspian where the water is cooler due to greater depth.

<span class="mw-page-title-main">Climate of Svalbard</span>

Svalbard is a Norwegian archipelago in the Arctic Ocean. The climate of Svalbard is principally a result of its latitude, which is between 74° and 81° north. Climate is defined by the World Meteorological Organization as the average weather over a 30-year period. The North Atlantic Current moderates Svalbard's temperatures, particularly during winter, giving it up to 20 °C (36 °F) higher winter temperature than similar latitudes in continental Russia and Canada. This keeps the surrounding waters open and navigable most of the year. The interior fjord areas and valleys, sheltered by the mountains, have fewer temperature differences than the coast, with about 2 °C lower summer temperatures and 3 °C higher winter temperatures. On the south of the largest island, Spitsbergen, the temperature is slightly higher than further north and west. During winter, the temperature difference between south and north is typically 5 °C, and about 3 °C in summer. Bear Island (Bjørnøya) has average temperatures even higher than the rest of the archipelago.

<span class="mw-page-title-main">Hauling-out</span> Marine mammal behaviour

Hauling-out is a behaviour associated with pinnipeds temporarily leaving the water. Hauling-out typically occurs between periods of foraging activity. Rather than remain in the water, pinnipeds haul-out onto land or sea-ice for reasons such as reproduction and rest. Hauling-out is necessary in seals for mating and giving birth. Other benefits of hauling-out may include predator avoidance, thermoregulation, social activity, parasite reduction and rest.

<span class="mw-page-title-main">Southern elephant seal</span> Species of marine mammal

The southern elephant seal is one of two species of elephant seals. It is the largest member of the clade Pinnipedia and the order Carnivora, as well as the largest extant marine mammal that is not a cetacean. It gets its name from its massive size and the large proboscis of the adult male, which is used to produce very loud roars, especially during the breeding season. A bull southern elephant seal is about 40% heavier than a male northern elephant seal, which is nearly twice the weight of a male walrus, or 6–7 times heavier than the largest living mostly terrestrial carnivorans, the Kodiak bear and the polar bear.

<i>Edwardsiella andrillae</i> Species of sea anemone

Edwardsiella andrillae is a species of sea anemone that uniquely lives anchored to the underside of sea ice offshore of Antarctica. It was discovered in December 2010 during a test run of an undersea robot by a team of researchers associated with the Antarctic Geological Drilling (ANDRILL) Program. The newly discovered anemone was named for the aforementioned program.

<span class="mw-page-title-main">Arctic ringed seal</span> Subspecies of carnivore

The Arctic ringed seal is a subspecies of ringed seals. Arctic ringed seals inhabit the Arctic Ocean, and are the most abundant and wide-ranging seal in the Northern Hemisphere. The ringed seal species is the smallest true seal, and gets its name from a distinctive patterning of light spots on dark grey colored fur. The ringed seal is commonly preyed upon by Polar bears, Arctic foxes, and Killer whales. Population estimates and survival rates are unknown, but average life expectancy is 15-28 years. Ringed seals have long been a component of the diet of indigenous people of the Arctic. Arctic ringed seals have been listed as threatened on the Endangered Species Act since 2012, and increasingly face loss of their habitat due to shrinking ice and snow cover.

References

  1. Redeker, K. R.; Chong, J. P. J.; Aguion, A.; Hodson, A.; Pearce, D. A. (2017-12-01). "Microbial metabolism directly affects trace gases in (sub) polar snowpacks". Journal of the Royal Society Interface. 14 (137): 20170729. doi:10.1098/rsif.2017.0729. ISSN   1742-5689. PMC   5746576 . PMID   29263129.
  2. Geiser, Fritz (2013). "Hibernation". Current Biology. 23 (5): R188–R193. Bibcode:2013CBio...23.R188G. doi: 10.1016/j.cub.2013.01.062 . PMID   23473557.
  3. Storey, Kenneth B.; Storey, Janet M. (2017). "Molecular Physiology of Freeze Tolerance in Vertebrates". Physiological Reviews. 97 (2): 623–665. doi: 10.1152/physrev.00016.2016 . PMID   28179395.
  4. 1 2 Johnston, David W.; Bowers, Matthew T.; Friedlaender, Ari S.; Lavigne, David M. (2012-01-04). "The Effects of Climate Change on Harp Seals (Pagophilus groenlandicus)". PLOS ONE. 7 (1): e29158. Bibcode:2012PLoSO...729158J. doi: 10.1371/journal.pone.0029158 . ISSN   1932-6203. PMC   3251559 . PMID   22238591.
  5. "NOAA". 27 January 2021.
  6. Burns, John J. (1970-08-01). "Remarks on the Distribution and Natural History of Pagophilic Pinnipeds in the Bering and Chukchi Seas". Journal of Mammalogy. 51 (3): 445–454. doi:10.2307/1378386. ISSN   0022-2372. JSTOR   1378386.
  7. 1 2 Perry, Elizabeth A.; Carr, Steven M.; Bartlett, Sylvia E.; Davidson, William S. (1995-02-23). "A Phylogenetic Perspective on the Evolution of Reproductive Behavior in Pagophilic Seals of the Northwest Atlantic as Indicated by Mitochondrial DNA Sequences". Journal of Mammalogy. 76 (1): 22–31. doi:10.2307/1382311. ISSN   0022-2372. JSTOR   1382311.
  8. 1 2 Holst, Meike; Stirling, Ian; Hobson, Keith A. (2001-10-01). "Diet of Ringed Seals (Phoca Hispida) on the East and West Sides of the North Water Polynya, Northern Baffin Bay". Marine Mammal Science. 17 (4): 888–908. Bibcode:2001MMamS..17..888H. doi:10.1111/j.1748-7692.2001.tb01304.x. ISSN   1748-7692.
  9. 1 2 Davis, R. W.; Fuiman, L. A.; Williams, T. M.; Collier, S. O.; Hagey, W. P.; Kanatous, S. B.; Kohin, S.; Horning, M. (1999-02-12). "Hunting Behavior of a Marine Mammal Beneath the Antarctic Fast Ice". Science. 283 (5404): 993–996. Bibcode:1999Sci...283..993D. doi:10.1126/science.283.5404.993. ISSN   0036-8075. PMID   9974394.
  10. Hanke, Frederike D.; Hanke, Wolf; Scholtyssek, Christine; Dehnhardt, Guido (2009-12-01). "Basic mechanisms in pinniped vision". Experimental Brain Research. 199 (3–4): 299–311. doi:10.1007/s00221-009-1793-6. ISSN   0014-4819. PMID   19396435. S2CID   23704640.
  11. Blix, Arnoldus Schytte (2016-04-15). "Adaptations to polar life in mammals and birds". Journal of Experimental Biology. 219 (8): 1093–1105. doi: 10.1242/jeb.120477 . ISSN   0022-0949. PMID   27103673.
  12. Mauritzen, Mette; Belikov, Stanislav E.; Boltunov, Andrei N.; Derocher, Andrew E.; Hansen, Edmond; Ims, Rolf A.; Wiig, Øystein; Yoccoz, Nigel (2003). "Functional Responses in Polar Bear Habitat Selection". Oikos. 100 (1): 112–124. Bibcode:2003Oikos.100..112M. doi:10.1034/j.1600-0706.2003.12056.x. JSTOR   3548267.
  13. 1 2 Hunt, G.L. (1991). "Marine birds and ice-influenced environments of polar oceans". Journal of Marine Systems. 2 (1–2): 233–240. Bibcode:1991JMS.....2..233H. doi:10.1016/0924-7963(91)90026-q.
  14. Horner, Rita; Ackley, Stephen F.; Dieckmann, Gerhard S.; Gulliksen, Bjorn; Hoshiai, Takao; Legendre, Louis; Melnikov, Igor A.; Reeburgh, William S.; Spindler, Michael (1992-09-01). "Ecology of sea ice biota". Polar Biology. 12 (3–4): 417–427. doi:10.1007/bf00243113. ISSN   0722-4060. S2CID   36412633.
  15. Poltermann, M. (2001-01-01). "Arctic sea ice as feeding ground for amphipods – food sources and strategies". Polar Biology. 24 (2): 89–96. Bibcode:2001PoBio..24...89P. doi:10.1007/s003000000177. ISSN   0722-4060. S2CID   8385527.
  16. Daly, Marymegan; Rack, Frank; Zook, Robert (2013-12-11). "Edwardsiella andrillae, a New Species of Sea Anemone from Antarctic Ice". PLOS ONE. 8 (12): e83476. Bibcode:2013PLoSO...883476D. doi: 10.1371/journal.pone.0083476 . ISSN   1932-6203. PMC   3859642 . PMID   24349517.
  17. 1 2 3 Hunter, Christine M.; Caswell, Hal; Runge, Michael C.; Regehr, Eric V.; Amstrup, Steve C.; Stirling, Ian (2010). "Climate change threatens polar bear populations: a stochastic demographic analysis". Ecology. 91 (10): 2883–2897. Bibcode:2010Ecol...91.2883H. doi:10.1890/09-1641.1. hdl: 1912/4685 . PMID   21058549.
  18. Kovacs, Kit M.; Lydersen, Christian (2008-07-01). "Climate change impacts on seals and whales in the North Atlantic Arctic and adjacent shelf seas". Science Progress. 91 (2): 117–150. doi: 10.3184/003685008x324010 . PMC   10367525 . PMID   18717366. S2CID   40115988.