Editing Arctic fox (section)

==Behavior==
[[File:Alopex lagopus IMG 9019.JPG|thumb|left|A sleeping Arctic fox with its tail wrapped around itself and over its face]]
Arctic foxes must endure a temperature difference of up to {{cvt|90-100|C-change}} between the external environment and their internal core temperature.<ref name="ReferenceC">{{cite journal|last1=Fuglesteg|first1=B. |author2=Haga, Ø.E. |name-list-style=amp |author3=Folkow, L.P. |author4=Fuglei, E. |author5=Blix, A.S. |title=Seasonal variations in basal metabolic rate, lower critical temperature and responses to temporary starvation in the arctic fox (''Alopex lagopus'') from Svalbard|journal=Polar Biology |date=2006 |volume=29 |issue=4 |pages=308–319|doi=10.1007/s00300-005-0054-9|bibcode=2006PoBio..29..308F |s2cid=31158070}}</ref> To prevent heat loss, the Arctic fox curls up tightly tucking its legs and head under its body and behind its furry tail. This position gives the fox the smallest surface area to volume ratio and protects the least insulated areas. Arctic foxes also stay warm by getting out of the wind and residing in their dens.<ref name="ReferenceD">{{cite journal|last1=Prestrud|first1=P. |s2cid=45830118|title=Adaptations by the Arctic Fox (''Alopex lagopus'') to the Polar Winter|journal=Arctic |date=1991|volume=44|issue=2|pages=132–138 |jstor=40511073|doi=10.14430/arctic1529}}</ref><ref name="ReferenceC" /> Although the Arctic foxes are active year-round and do not hibernate, they attempt to preserve fat by reducing their locomotor activity.<ref name="ReferenceD" /><ref name="ReferenceE">{{cite journal |last1=Klir|first1=J. |last2=Heath|first2=J. |name-list-style=amp |title=An Infrared Thermographic Study of Surface Temperature in Relation to External Thermal Stress in Three Species of Foxes: The Red Fox (''Vulpes vulpes''), Arctic Fox (''Alopex lagopus''), and Kit Fox (''Vulpes macrotis'') |journal=Physiological Zoology|date=1991|volume=65|issue=5|pages=1011–1021 |jstor=30158555|doi=10.1086/physzool.65.5.30158555|s2cid=87183522}}</ref> They build up their fat reserves in the autumn, sometimes increasing their body weight by more than 50%. This provides greater insulation during the winter and a source of energy when food is scarce.<ref name="NOAA" />

===Reproduction===
In the spring, the Arctic fox's attention switches to reproduction and a home for their potential offspring. They live in large dens in frost-free, slightly raised ground. These are complex systems of tunnels covering as much as {{cvt|1000|m2}} and are often in [[esker]]s, long ridges of sedimentary material deposited in formerly [[Glacier|glaciated]] regions. These dens may be in existence for many decades and are used by many generations of foxes.<ref name="NOAA" />

[[File:Fox pups animals.jpg|thumb|Pups of Arctic fox with summer morph]]
Arctic foxes tend to select dens that are easily accessible with many entrances, and that are clear from snow and ice making it easier to burrow in. The Arctic fox builds and chooses dens that face southward towards the sun, which makes the den warmer. Arctic foxes prefer large, maze-like dens for predator evasion and a quick escape especially when red foxes are in the area. Natal dens are typically found in rugged terrain, which may provide more protection for the pups. But, the parents will also relocate litters to nearby dens to avoid predators. When red foxes are not in the region, Arctic foxes will use dens that the red fox previously occupied. Shelter quality is more important to the Arctic fox than the proximity of spring prey to a den.<ref name="ReferenceB" />

The main prey of the Arctic fox in the tundra are lemmings, which is why the white fox is often called the "lemming fox". The white fox's reproduction rates reflect the lemming population density, which cyclically fluctuates every 3–5 years.<ref name="dx.doi.org">{{cite journal|last1=Pagh|first1=S. |last2=Hersteinsson|first2=P. |name-list-style=amp|title=Difference in diet and age structure of blue and white Arctic foxes (''Vulpes lagopus'') in the Disko Bay area, West Greenland|journal=Polar Research|date=2008|volume=27|issue=1|pages=44–51 |doi=10.1111/j.1751-8369.2008.00042.x|bibcode=2008PolRe..27...44P|s2cid=129105385|doi-access=free}}</ref><ref name="doi.org" /> When lemmings are abundant, the white fox can give birth to 18 pups, but they often do not reproduce when food is scarce. The "coastal fox" or blue fox lives in an environment where food availability is relatively consistent, and they will have up to 5 pups every year.<ref name="doi.org" />

Breeding usually takes place in April and May, and the [[gestation period]] is about 52 days. Litters may contain as many as 25 (the largest litter size in the [[Order (biology)|order]] [[Carnivora]]).<ref>{{cite book|last=MacDonald|first=David W.|title=Biology and Conservation of Wild Canids|year=2004|publisher=Oxford University Press|isbn=978-0-19-851556-2}}</ref> The young emerge from the den when 3 to 4 weeks old and are weaned by 9 weeks of age.<ref name="NOAA" />

Arctic foxes are primarily [[Monogamy in animals|monogamous]] and both parents will care for the offspring. When predators and prey are abundant, Arctic foxes are more likely to be promiscuous (exhibited in both males and females) and display more complex social structures. Larger packs of foxes consisting of breeding or non-breeding males or females can guard a single territory more proficiently to increase pup survival. When resources are scarce, competition increases and the number of foxes in a territory decreases. On the coasts of [[Svalbard]], the frequency of complex social structures is larger than inland foxes that remain monogamous due to food availability. In Scandinavia, there are more complex social structures compared to other populations due to the presence of the red fox. Also, conservationists are supplying the declining population with supplemental food. One unique case, however, is [[Iceland]] where monogamy is the most prevalent. The older offspring (1-year-olds) often remain within their parent's territory even though predators are absent and there are fewer resources, which may indicate [[kin selection]] in the fox.<ref name="doi.org" />

===Diet===
[[File:Fox with fish.jpg|thumb|An Arctic fox (summer morph) with [[salmon]]]]
Arctic foxes generally eat any small animal they can find, including [[lemming]]s, [[vole]]s, other rodents, [[hare]]s, [[bird]]s, [[Egg (food)|eggs]], fish, and [[carrion]]. They scavenge on carcasses left by larger predators such as wolves and [[polar bear]]s, and in times of scarcity also eat their [[feces]]. In areas where they are present, lemmings are their most common prey,<ref name="NOAA" /> and a family of foxes can eat dozens of lemmings each day. In some locations in northern Canada, a high seasonal abundance of migrating birds that breed in the area may provide an important food source. On the coast of Iceland and other islands, their diet consists predominantly of birds. During April and May, the Arctic fox also preys on [[ringed seal]] pups when the young animals are confined to a snow den and are relatively helpless. They also consume berries and seaweed, so they may be considered [[omnivore]]s.<ref name="Bockstoce2009">{{cite book|author=Bockstoce, J.R.|title=Furs and frontiers in the far north: the contest among native and foreign nations for the Bering Strait fur trade |year=2009 |url=https://books.google.com/books?id=HY6LvFMSxxwC&pg=PA41|publisher=Yale University Press |isbn=978-0-300-14921-0 |page=41}}</ref> This fox is a significant bird-egg predator, consuming eggs of all except the largest tundra bird species.<ref name="truett">{{cite book|editor1=Truett, J.C. |editor2=Johnson, S.R. |title=The natural history of an Arctic oil field: development and the biota |year=2000 |publisher=Academic Press |place=San Diego, San Francisco |isbn=978-0-12-701235-3 |chapter=Arctic Fox |pages=159–178 |author=Burgess, R. |chapter-url=https://books.google.com/books?id=ELsq-yAP0XkC&pg=PA161}}</ref>

Arctic foxes survive harsh winters and food scarcity by either hoarding food or storing body fat subcutaneously and viscerally. At the beginning of winter, one Arctic fox has approximately 14740 kJ of energy storage from fat alone. Using the lowest BMR value measured in Arctic foxes, an average sized fox of {{cvt|3.5|kg}} would need 471 kJ/day during the winter to survive. In Canada, Arctic foxes acquire from [[snow goose]] eggs at a rate of 2.7–7.3 eggs/h and store 80–97% of them. Scats provide evidence that they eat the eggs during the winter after caching. Isotope analysis shows that eggs can still be eaten after a year, and the metabolizable energy of a stored goose egg only decreases by 11% after 60 days; a fresh egg has about 816 kJ. Eggs stored in the summer are accessed the following spring prior to reproduction.<ref>{{cite journal |last1=Careau|first1=V. |s2cid=51683546 |author2=Giroux, J.F. |author3=Gauthier, G. |author4=Berteaux, D. |name-list-style=amp |title=Surviving on cached foods — the energetics of egg-caching by Arctic foxes |journal=Canadian Journal of Zoology |date=2008 |volume=86|issue=10|pages=1217–1223 |doi=10.1139/Z08-102|bibcode=2008CaJZ...86.1217C }}</ref>