Editing Arctic fox (section)

==Adaptations==
The Arctic fox lives in some of the most frigid extremes on the planet, but they do not start to shiver until the temperature drops to {{cvt|-70|°C}}. Among its [[adaptation]]s for survival in the cold is its dense, multilayered [[pelage]], which provides excellent insulation.<ref name="smith"/><ref>Claudio Sillero-Zubiri, Michael Hoffmann and David W. Macdonald (eds.) (2004). [http://www.carnivoreconservation.org/files/actionplans/canids.pdf Canids: Foxes, Wolves, Jackals and Dogs] {{webarchive|url=https://web.archive.org/web/20150923200655/http://www.carnivoreconservation.org/files/actionplans/canids.pdf |date=23 September 2015 }}. IUCN/SSC Canid Specialist Group.</ref> Additionally, the Arctic fox is the only canid whose foot pads are covered in fur. There are two genetically distinct coat color [[Polymorphism (biology)|morphs]]: white and blue.<ref name="ReferenceD"/> The white morph has [[seasonal camouflage]], white in winter and brown along the back with light grey around the abdomen in summer. The blue morph is often a dark blue, brown, or grey color year-round. Although the blue [[allele]] is dominant over the white allele, 99% of the Arctic fox population is the white morph.<ref name="doi.org"/><ref name="dx.doi.org"/> Two similar mutations to [[MC1R]] cause the blue color and the lack of seasonal color change.<ref name=Vage2005>{{cite journal | title = Two cysteine substitutions in the MC1R generate the blue variant of the arctic fox (Alopex lagopus) and prevent expression of the white winter coat | year = 2005| doi = 10.1016/j.peptides.2004.11.040| last1 = Våge| first1 = D.I.| last2=Fuglei| first2 = E.| last3 = Snipstad| first3 = K. | last4 = Beheim| first4 = J. | last5 = Landsem| first5 = V.M. |last6=Klungland| first6 = H. | journal = Peptides| volume = 26| issue = 10| pages = 1814–1817| pmid = 15982782| hdl = 11250/174384| s2cid = 7264542| hdl-access = free}}</ref> The fur of the Arctic fox provides the best insulation of any mammal.<ref name="ADAPT">{{cite web |url=http://pubs.aina.ucalgary.ca/arctic/arctic44-2-132.pdf|title=Adaptations by the arctic fox to the polar winter|access-date=2015-10-08|publisher=Arctic, vol.44 no.2|url-status=live|archive-url=https://web.archive.org/web/20160304201957/http://pubs.aina.ucalgary.ca/arctic/arctic44-2-132.pdf|archive-date=4 March 2016|df=dmy-all}}</ref>

The Arctic fox has a low [[surface area to volume ratio]], as evidenced by its generally compact body shape, short muzzle and legs, and short, thick ears. Since less of its surface area is exposed to the Arctic cold, less heat escapes from its body.<ref name="DECGNL">[http://www.env.gov.nl.ca/env/snp/programs/education/animal_facts/mammals/arctic_fox.html Arctic Fox ''Alopex lagopus''] {{webarchive|url=https://web.archive.org/web/20160305031515/http://www.env.gov.nl.ca/env/snp/programs/education/animal_facts/mammals/arctic_fox.html |date=5 March 2016 }}. Department of Environment and Conservation, Government of Newfoundland and Labrador</ref>

===Sensory modalities===
The Arctic fox has a functional [[hearing range]] between 125&nbsp;Hz–16&nbsp;kHz with a sensitivity that is ≤ 60&nbsp;dB in air, and an average peak sensitivity of 24&nbsp;dB at 4&nbsp;kHz. Overall, the Arctic foxes hearing is less sensitive than the dog and the kit fox. The Arctic fox and the kit fox have a low upper-frequency limit compared to the domestic dog and other carnivores.<ref>{{cite journal |last1=Stansbury|first1=A. |author2=Thomas, J.A. |name-list-style=amp |author3=Stalf, C.E. |author4= Murphy, L.D. |author5=Lombardi, D. |author6=Carpenter, J. |author7=Mueller, T. |title=Behavioral audiogram of two Arctic foxes (''Vulpes lagopus'') |journal=Polar Biology |date=2014|volume=37|issue=3|pages=417–422|doi=10.1007/s00300-014-1446-5|bibcode=2014PoBio..37..417S |s2cid=17154503}}</ref> The Arctic fox can easily hear lemmings burrowing under 4-5 inches of snow.<ref>{{cite book|last1=Perry|first1=Richard|title=The Polar Worlds|date=1973|publisher=Taplinger Pub. Co., Inc. |location=New York, New York|isbn=978-0800864057|pages=188 |edition=First |url=https://archive.org/details/polarworlds0000perr/page/188}}</ref> When it has located its prey, it pounces and punches through the snow to catch its prey.<ref name="DECGNL"/>

The Arctic fox also has a keen sense of smell. They can smell carcasses that are often left by polar bears anywhere from {{cvt|10|to|40|km}}. It is possible that they use their sense of smell to also track down polar bears. Additionally, Arctic foxes can smell and find frozen lemmings under {{cvt|46|–|77|cm}} of snow, and can detect a subnivean seal lair under {{cvt|150|cm}} of snow.<ref>{{cite journal |last1=Lai|first1=S. |last2=Bety|first2=J. |last3=Berteaux|first3=D. |name-list-style=amp |title=Spatio–temporal hotspots of satellite– tracked arctic foxes reveal a large detection range in a mammalian predator|journal=Movement Ecology |date=2015 |volume=3 |issue=37 |pages=37|doi=10.1186/s40462-015-0065-2|pmid=26568827|pmc=4644628 |bibcode=2015MvEco...3...37L |doi-access=free }}</ref>

===Physiology===
[[File:Arctic fox lying in grass - DPLA - 6bbdf7a6ee8c38192bcfad0a6f6dab84.jpg|left|thumb|Arctic fox lying in grass. A fox's thick winter coat helps keep its body temperature near {{cvt|100|F|order=flip}}. Foxes also have fur on the soles of their feet and reduced blood flow to their legs to help keep them warm.]]
The Arctic fox contains advantageous genes to overcome extreme cold and starvation periods. [[Transcriptome]] [[sequencing]] has identified two genes that are under [[positive selection]]: [[Glycolipid transfer protein]] domain containing 1 (GLTPD1) and [[V-akt murine thymoma viral oncogene homolog 2]] (AKT2). GLTPD1 is involved in the [[fatty acid metabolism]], while AKT2 pertains to the glucose metabolism and insulin signaling.<ref name="ReferenceF">{{cite journal|last1=Kumar|first1=V. |author2=Kutschera, V.E. |author3=Nilsson, M.A. |author4=Janke, A. |name-list-style=amp |title=Genetic signatures of adaptation revealed from transcriptome sequencing of Arctic and red foxes |journal=BMC Genomics |date=2015 |volume=16 |issue=1 |pages=585 |doi=10.1186/s12864-015-1724-9 |pmid=26250829 |pmc=4528681 |doi-access=free }}</ref>

The average mass specific [[Basal metabolic rate|BMR]] and total BMR are 37% and 27% lower in the winter than the summer. The Arctic fox decreases its BMR via metabolic depression in the winter to conserve fat storage and minimize energy requirements. According to the most recent data, the lower critical temperature of the Arctic fox is at {{cvt|−7|C}} in the winter and {{cvt|5|C}} in the summer. It was commonly believed that the Arctic fox had a lower critical temperature below {{cvt|−40|C}}. However, some scientists have concluded that this statistic is not accurate since it was never tested using the proper equipment.<ref name="ReferenceC"/>

About 22% of the total body surface area of the Arctic fox dissipates heat readily compared to red foxes at 33%. The regions that have the greatest heat loss are the nose, ears, legs, and feet, which is useful in the summer for thermal heat regulation. Also, the Arctic fox has a beneficial mechanism in their nose for evaporative cooling like dogs, which keeps the brain cool during the summer and exercise.<ref name="ReferenceE"/> The [[thermal conductivity]] of [[Arctic fox fur]] in the summer and winter is the same; however, the thermal conductance of the Arctic fox in the winter is lower than the summer since fur thickness increases by 140%. In the summer, the thermal conductance of the Arctic foxes body is 114% higher than the winter, but their body core temperature is constant year-round.

One way that Arctic foxes regulate their body temperature is by utilizing a countercurrent heat exchange in the blood of their legs.<ref name="ReferenceC"/> Arctic foxes can constantly keep their feet above the tissue freezing point ({{cvt|−1|C}}) when standing on cold substrates without losing mobility or feeling pain. They do this by increasing vasodilation and blood flow to a capillary rete in the pad surface, which is in direct contact with the snow rather than the entire foot. They selectively vasoconstrict blood vessels in the center of the foot pad, which conserves energy and minimizes heat loss.<ref name="ReferenceE"/><ref name="ReferenceG">{{cite journal |last1=Henshaw|first1=R. |last2=Underwood|first2=L. |last3=Casey|first3=T. |title=Peripheral Thermoregulation: Foot Temperature in Two Arctic Canines |journal=Science |date=1972|volume=175 |issue=4025 |pages=988–990 |jstor=1732725 |bibcode=1972Sci...175..988H |doi=10.1126/science.175.4025.988 |pmid=5009400|s2cid=23126602}}</ref> Arctic foxes maintain the temperature in their paws independently from the core temperature. If the core temperature drops, the pad of the foot will remain constantly above the tissue freezing point.<ref name="ReferenceG"/>