![Polar Bear AdF](https://upload.wikimedia.org/wikipedia/commons/3/3d/Polar_Bear_AdF.jpg)
Pagophily or pagophilia is the preference or dependence on
water ice Water ice could refer to:
* Ice formed by water (as opposed to other substances)
*The alternate term for various similar frozen fruit-flavoured desserts:
** Italian ice primarily in Philadelphia and the Delaware Valley
**Sorbet
Sorbet (), also ...
for some or all activities and functions. The term ''Pagophila'' is derived from the
Ancient Greek
Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...
''pagos'' meaning "sea-ice", and ''philos'' meaning "-loving".
Pagophilic animals, plants, etc. prefer to live in ice or perform certain activities in the ice. For example, a number of
ice seals Ice seal, or (in the Southern Hemisphere) pack-ice seal is a general term applied to any one of a number of pinniped species of the family Phocidae whose life cycle is completed largely on or about the sea ice of the Earth's polar regions.
The ...
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.
The Evolutionary and Adaptive Basis of Pagophily
The dependence and preference for ice and snow is believed to have an evolutionary basis dating back to the last
ice age
An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gree ...
, 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. Survival in extreme habitats such as ice habitats is possible due to behavioural and/ or physiological adaptations. These adaptations may include;
hibernation
Hibernation is a state of minimal activity and metabolic depression undergone by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It most ...
, insulation in the form of fat or blubber, increase hair or feather growth, or the presence of an anti-freeze-like enzyme.
Phagophily 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.
Pagophily 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.
According to the
National Oceanic and Atmospheric Administration
The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditio ...
ice seals are found in the Arctic and Antarctic. 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 harp seal pup](https://upload.wikimedia.org/wikipedia/commons/d/db/Weaned_harp_seal_pup.jpg)
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 seal
The grey seal (''Halichoerus grypus'') is found on both shores of the North Atlantic Ocean. In Latin Halichoerus grypus means "hook-nosed sea pig". It is a large seal of the family Phocidae, which are commonly referred to as "true seals" or " ...
s,
hooded seal
The hooded seal (''Cystophora cristata'') is a large phocid found only in the central and western North Atlantic, ranging from Svalbard in the east to the Gulf of St. Lawrence in the west. The seals are typically silver-grey or white in color, w ...
s and
harp seal
The harp seal (''Pagophilus groenlandicus''), 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 ...
s. 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.
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.
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.
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
invertebrate
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
s 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.
Diving behaviour is critical for hunting in adult seals.
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.
The adaptation of amphibious seal vision has contributed to the evolution of pagophilia in seals.
''
Ursus maritimus
The polar bear (''Ursus maritimus'') is a hypercarnivorous bear whose native range lies largely within the Arctic Circle, encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is the largest extant bear spec ...
''
![Polar bear (Ursus maritimus) with its prey](https://upload.wikimedia.org/wikipedia/commons/5/5e/Polar_bear_%28Ursus_maritimus%29_with_its_prey.jpg)
''Ursus Maritimus'', commonly called
polar bears
The polar bear (''Ursus maritimus'') is a hypercarnivorous bear whose native range lies largely within the Arctic Circle, encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is the largest extant bear species ...
, are 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
Fast ice (also called ''land-fast ice'', ''landfast ice'', and ''shore-fast ice'') is sea ice that is "fastened" to the coastline, to the sea floor along shoals or to grounded icebergs.Leppäranta, M. 2011. The Drift of Sea Ice. Berlin: Springer ...
.
''
Ursus Maritimus
The polar bear (''Ursus maritimus'') is a hypercarnivorous bear whose native range lies largely within the Arctic Circle, encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is the largest extant bear spec ...
'' possess a number of adaptations to allow them to survive in harsh, cold environments. These
thermoregulatory
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...
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
Blubber is a thick layer of vascularized adipose tissue under the skin of all cetaceans, pinnipeds, penguins, and sirenians.
Description
Lipid-rich, collagen fiber-laced blubber comprises the hypodermis and covers the whole body, except for pa ...
.
Pagophily in Birds
Several species of marine birds live on ice caps in both the
Arctic
The Arctic ( or ) is a polar regions of Earth, polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenla ...
and
Antarctic
The Antarctic ( or , American English also or ; commonly ) is a polar region around Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica, the Kerguelen Plateau and other ...
.
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
Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...
,
algae
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
and small fish live directly under
sea ice
Sea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface (as does fresh water ice, which has an even lower density). Sea ice covers about 7% of the Earth's surface and about 12% of the world's oce ...
. Access to enhanced foraging opportunities is a plausible explanation for pagophily in marine birds.
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 (''Pagophila eburnea'') is a small gull, the only species in the genus ''Pagophila''. It breeds in the high Arctic and has a circumpolar distribution through Greenland, northernmost North America, and Eurasia.
Taxonomy
The ivory ...
. The ivory gull is found in the
Arctic
The Arctic ( or ) is a polar regions of Earth, polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenla ...
in the northernmost parts of Europe and North America.
Ivory gulls feed on
crustaceans
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...
, fish and rodents and are also considered opportunistic
scavengers
Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding b ...
. The gulls often follow pagophilic mammals such as
seals
Seals may refer to:
* Pinniped, a diverse group of semi-aquatic marine mammals, many of which are commonly called seals, particularly:
** Earless seal, or "true seal"
** Fur seal
* Seal (emblem), a device to impress an emblem, used as a means of a ...
and
polar bears
The polar bear (''Ursus maritimus'') is a hypercarnivorous bear whose native range lies largely within the Arctic Circle, encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is the largest extant bear species ...
and feed on the remains of their prey.
Pagophily in
Invertebrate
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
s
![Edwardsiella andrillae by ROV SCINI retraitée FL](https://upload.wikimedia.org/wikipedia/commons/5/53/Edwardsiella_andrillae_by_ROV_SCINI_retrait%C3%A9e_FL.png)
Sea ice invertebrates serve as important food sources for many Pagophilic
vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
species.
''Gammarus wilkitzkii''
''
Gammarus
''Gammarus'' is an amphipod crustacean genus in the family Gammaridae. It contains more than 200 described species, making it one of the most species-rich genera of crustaceans. Different species have different optimal conditions, particularly i ...
wilkitzkii'' is an
amphipod
Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far descr ...
species that lives below Arctic sea ice. This organism uses a relatively wide variety of food sources including
detritus
In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...
, sea
algae
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
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.
''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.
Climate Change and Pagophilic Animals
Climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
and the reduction of sea ice in
polar regions
The polar regions, also called the frigid zones or polar zones, of Earth are the regions of the planet that surround its geographical poles (the North and South Poles), lying within the polar circles. These high latitudes are dominated by float ...
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.
These projections were important in the decision to list the polar bear as a threatened species under the U.S.
Endangered Species Act.
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
ill impactdistributional changes and in all probability abundance reductions".
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.
Climate change poses a significant threat to pagophilic animals.
See also
*
Pagophila
*
Sea ice
Sea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface (as does fresh water ice, which has an even lower density). Sea ice covers about 7% of the Earth's surface and about 12% of the world's oce ...
*
Arctic
The Arctic ( or ) is a polar regions of Earth, polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenla ...
*
Antarctic
The Antarctic ( or , American English also or ; commonly ) is a polar region around Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica, the Kerguelen Plateau and other ...
*
Climate Change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
References
{{Reflist
Ethology
Water ice