Editing Frog (section)

===Torpor===
During extreme conditions, some frogs enter a state of [[torpor]] and remain inactive for months. In colder regions, many species of frog [[Hibernation|hibernate]] in winter. Those that live on land such as the [[American toad]] (''Bufo americanus'') dig a burrow and make a [[Hibernaculum (zoology)|hibernaculum]] in which to lie [[Dormancy|dormant]]. Others, less proficient at digging, find a crevice or bury themselves in dead leaves. Aquatic species such as the [[American bullfrog]] (''Rana catesbeiana'') normally sink to the bottom of the pond where they lie, semi-immersed in mud but still able to access the oxygen dissolved in the water. Their metabolism slows down and they live on their energy reserves. Some frogs such as the [[wood frog]], [[moor frog]], or [[spring peeper]] can even survive being frozen. Ice crystals form under the skin and in the body cavity but the essential organs are protected from freezing by a high concentration of glucose. An apparently lifeless, frozen frog can resume respiration and its heartbeat can restart when conditions warm up.<ref>{{cite magazine |url=http://www.scientificamerican.com/article.cfm?id=how-do-frogs-survive-wint |title=How do frogs survive winter? Why don't they freeze to death? |author=Emmer, Rick |date=November 24, 1997 |magazine=Scientific American |access-date=June 15, 2012}}</ref>

At the other extreme, the [[striped burrowing frog]] (''Cyclorana alboguttata'') regularly [[Aestivation|aestivates]] during the hot, dry season in Australia, surviving in a dormant state without access to food and water for nine or ten months of the year. It burrows underground and curls up inside a protective [[Cocoon (silk)|cocoon]] formed by its shed skin. Researchers at the [[University of Queensland]] have found that during aestivation, the [[metabolism]] of the frog is altered and the operational efficiency of the [[mitochondria]] is increased. This means that the limited amount of energy available to the comatose frog is used in a more efficient manner. This survival mechanism is only useful to animals that remain completely unconscious for an extended period of time and whose energy requirements are low because they are cold-blooded and have no need to generate heat.<ref>{{cite journal |author1=Kayes, Sara M. |author2=Cramp, Rebecca L. |author3=Franklin, Craig E. |year=2009 |title=Metabolic depression during aestivation in ''Cyclorana alboguttata'' |journal=Comparative Biochemistry and Physiology&nbsp;– Part A: Molecular & Integrative Physiology |volume=154 |issue=4 |pages=557–563 |doi=10.1016/j.cbpa.2009.09.001 |pmid=19737622 }}</ref> Other research showed that, to provide these energy requirements, muscles atrophy, but hind limb muscles are preferentially unaffected.<ref>{{cite journal |author1=Hudson, N. J. |author2=Lehnert, S. A. |author3=Ingham, A. B. |author4=Symonds, B. |author5=Franklin, C. E. |author6=Harper, G. S. |year=2005 |title=Lessons from an estivating frog: sparing muscle protein despite starvation and disuse |journal=[[American Journal of Physiology|AJP: Regulatory, Integrative and Comparative Physiology]] |volume=290 |issue=3 |pages = R836–R843 | doi = 10.1152/ajpregu.00380.2005 | pmid = 16239372 |s2cid=8395980 }}</ref> Frogs have been found to have upper critical temperatures of around 41 degrees Celsius.<ref>{{Cite book|title=Environmental Physiology of Animals|last=Wilmer|first=Pat|publisher=Wiley|year=2009|isbn=9781405107242|pages=[https://archive.org/details/environmentalphy00will/page/188 188]|url=https://archive.org/details/environmentalphy00will/page/188}}</ref>