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Torpor
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Torpor is a state of decreased physiological activity in an animal, usually marked by a reduced body temperature and metabolic rate. Torpor enables animals to survive periods of reduced food availability.[1] The term "torpor" can refer to the time a hibernator spends at low body temperature, lasting days to weeks, or it can refer to a period of low body temperature and metabolism lasting less than 24 hours, as in "daily torpor".
Animals that undergo daily torpor include birds (even tiny hummingbirds, notably Cypselomorphae)[2][3] and some mammals, including many marsupial species,[4][5] rodent species (such as mice), and bats.[6] During the active part of their day, such animals maintain normal body temperature and activity levels, but their metabolic rate and body temperature drop during a portion of the day (usually night) to conserve energy.[citation needed]
Some animals seasonally go into long periods of inactivity, with reduced body temperature and metabolism, made up of multiple bouts of torpor. This is known as hibernation if it occurs during winter or aestivation if it occurs during the summer. Daily torpor, on the other hand, is not seasonally dependent and can be an important part of energy conservation at any time of year.[7]
Torpor is a well-controlled thermoregulatory process and not, as previously thought, the result of switching off thermoregulation.[8] Marsupial torpor differs from non-marsupial mammalian (eutherian) torpor in the characteristics of arousal. Eutherian arousal relies on a heat-producing brown adipose tissue as a mechanism to accelerate rewarming. The mechanism of marsupial arousal is unknown, but appears not to rely on brown adipose tissue.[9]
- ^ Vuarin, Pauline; Dammhahn, Melanie; Kappeler, Peter M.; Henry, Pierre-Yves (September 2015). "When to initiate torpor use? Food availability times the transition to winter phenotype in a tropical heterotherm" (PDF). Oecologia. 179 (1): 43–53. Bibcode:2015Oecol.179...43V. doi:10.1007/s00442-015-3328-0. PMID 25953115. S2CID 17050304.
- ^ Hainsworth, F. R.; Wolf, L. L. (17 April 1970). "Regulation of Oxygen Consumption and Body Temperature during Torpor in a Hummingbird, Eulampis jugularls". Science. 168 (3929): 368–369. Bibcode:1970Sci...168..368R. doi:10.1126/science.168.3929.368. PMID 5435893. S2CID 30793291.
- ^ "Hummingbirds". Migratory Bird Center, Smithsonian National Zoological Park. Archived from the original on 2008-02-14.
- ^ Geiser, F (1994). "Hibernation and Daily Torpor in Marsupials - a Review". Australian Journal of Zoology. 42 (1): 1. doi:10.1071/zo9940001. S2CID 84914662.
- ^ Stannard, H.J.; Fabian, M.; Old, J.M. (2015). "To bask or not to bask: Behavioural thermoregulation in two species of dasyurid, Phascogale calura and Antechinomys laniger". Journal of Thermal Biology. 53: 66–71. Bibcode:2015JTBio..53...66S. doi:10.1016/j.jtherbio.2015.08.012. PMID 26590457.
- ^ Bartels, W.; Law, B. S.; Geiser, F. (7 April 1998). "Daily torpor and energetics in a tropical mammal, the northern blossom-bat Macroglossus minimus (Megachiroptera)". Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology. 168 (3): 233–239. doi:10.1007/s003600050141. PMID 9591364. S2CID 16870476.
- ^ "Wikipedia, the free encyclopedia". www.wikipedia.org. Retrieved 2024-03-22.
- ^ Geiser, Fritz (March 2004). "Metabolic Rate and Body Temperature Reduction During Hibernation and Daily Torpor". Annual Review of Physiology. 66 (1): 239–274. doi:10.1146/annurev.physiol.66.032102.115105. PMID 14977403. S2CID 22397415.
- ^ Dawson, T. J.; Finch, E.; Freedman, L.; Hume, I. D.; Renfree, Marilyn; Temple-Smith, P. D. "Morphology and Physiology of the Metatheria" (PDF). In Walton, D. W.; Richardson, B. J. (eds.). Fauna of Australia - Volume 1B Mammalia. ISBN 978-0-644-06056-1.
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