Torpor is a state of decreased physiological activity in an animal, usually 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] rodent species (such as mice), and bats.[5] During the active part of their day, such animals maintain normal body temperature and activity levels, but their metabolic rate and body temperature drops during a portion of the day (usually night) to conserve energy. Torpor is often used to help animals survive during periods of colder temperatures, as it allows them to save the energy that would normally be used to maintain a high body temperature.

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.

Torpor is a well-controlled thermoregulatory process and not, as previously thought, the result of switching off thermoregulation.[6] 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.[7]


The evolution of torpor likely accompanied the development of homeothermy.[8] Animals capable of maintaining a body temperature above ambient temperature when other members of its species could not would have a fitness advantage. Benefits of maintaining internal temperatures include increased foraging time and less susceptibility to extreme drops in temperature.[8] This adaptation of increasing body temperature to forage has been observed in small nocturnal mammals when they first wake up in the evening.[9][10][11]

Although homeothermy lends advantages such as increased activity levels, small mammals and birds maintaining an internal body temperature spend up to 100 times more energy in low ambient temperatures compared to ectotherms.[12] To cope with this challenge, these animals maintain a much lower body temperature, staying just over ambient temperature rather than at normal operating temperature. This reduction in body temperature and metabolic rate allows the prolonged survival of animals capable of entering torpid states.


Slowing metabolic rate to conserve energy in times of insufficient resources is the primarily noted purpose of torpor.[13] This conclusion is largely based on laboratory studies where torpor was observed to follow food deprivation.[14] There is evidence for other adaptive functions of torpor where animals are observed in natural contexts:

Fat conservation observed in small birds

Torpor has been shown to be a strategy of small migrant birds to increase their body fat. Hummingbirds, resting at night during migration, were observed to enter torpor which helped conserve fat stores for the rest of their migration.[14]

This strategy of using torpor to increase body fat has also been observed in wintering chickadees.[15] Black-capped chickadees, living in temperate forests of North America, do not migrate south during winter. The chickadee can maintain a body temperature 12 °C lower than normal. This reduction in metabolism allows it to conserve 30% of fat stores amassed from the previous day. Without using torpor the chickadee would not be able to conserve its fat stores to survive winter.

Advantage in environments with unpredictable food sources

Torpor can be a strategy of animals with unpredictable food supplies.[16] For example, high-latitude living rodents use torpor seasonally when not reproducing. These rodents use torpor as means to survive winter and live to reproduce in the next reproduction cycle when food sources are plentiful, separating periods of torpor from the reproduction period. Some animals use torpor during their reproductive cycle, as seen in unpredictable habitats.[16] They experience the cost of a prolonged reproduction period but the payoff is survival to be able to reproduce at all.[16]

The eastern long-eared bat uses torpor during winter and is able to arouse and forage during warm periods.[17]

Survival during mass extinctions

It is suggested that this daily torpor use may have allowed survival through mass extinction events.[18] Heterotherms make up only four out of 61 mammals confirmed to have gone extinct over the last 500 years.[18] Torpor enables animals to reduce energy requirements allowing them to better survive harsh conditions.

Inter-species competition

Interspecific competition occurs when two species require the same resource for energy production.[19] Torpor increases fitness in the case of inter-specific competition with the nocturnal common spiny mouse.[19] When the golden spiny mouse experiences reduced food availability by diet overlap with the common spiny mouse it spends more time in a torpid state.

Parasite resistance by bats

A drop in temperature from torpor has been shown to reduce the ability of parasites to reproduce.[20] Ectoparasites of bats in temperate zones have reduced reproductive rates when bats enter torpor. Where bats do not enter torpor the parasites reproduce at a constant rate throughout the year.

NASA deep sleep option for a mission to Mars

In 2013, NASA began researching a way to dramatically cut the cost of a human expedition to Mars by putting the crew in extended torpor for 90 to 180 days. Traveling while hibernating would reduce astronauts' metabolic functions and minimize requirements for life support during multi-year missions.[21]

See also


  1. ^ Vuarin, Pauline; Dammhahn, Melanie; Kappeler, Peter M.; Henry, Pierre-Yves (2015). "When to initiate torpor use? Food availability times the transition to winter phenotype in a tropical heterotherm". Oecologia. 179 (1): 43–53. doi:10.1007/s00442-015-3328-0. PMID 25953115.
  2. ^ Hainsworth, F.R.; Wolf, L.L. (1970). "Regulation of oxygen consumption and body temperature during torpor in a hummingbird, Eulampis jugularis". Science. 168 (3929): 368–369. doi:10.1126/science.168.3929.368. PMID 5435893.
  3. ^ "Hummingbirds". Migratory Bird Center, Smithsonian National Zoological Park. Archived from the original on 2008-02-14.
  4. ^ Geiser, Fritz (1994). "Hibernation and Daily Torpor in Marsupials – a Review". Australian Journal of Zoology. 42 (1): 1–16. doi:10.1071/zo9940001.
  5. ^ Bartels, W.; Law, B.S.; Geiser, F. (1998). "Daily torpor and energetics in a tropical mammal, the northern blossom-bat Macroglossus minimus (Megachiroptera)". J. Comp. Physiol. B. 168 (3): 233–239. doi:10.1007/s003600050141. PMID 9591364.
  6. ^ Geiser, Fritz (2004). "Metabolic Rate and Body Temperature Reduction During Hibernation and Daily Torpor". Annu. Rev. Physiol. 66 (66): 239–274. doi:10.1146/annurev.physiol.66.032102.115105. PMID 14977403.
  7. ^ Dawson, T.J., et al. (eds.); Fauna of Australia Vol. 1b – Mammalia; 17. Morphology and Physiology of the Metatheria; pp. 102, p. 30
  8. ^ a b Geiser, Fritz; Stawski, Clare; Wacker, Chris B.; Nowack, Julia (2017). "Phoenix from the Ashes: Fire, Torpor, and the Evolution of Mammalian Endothermy". Frontiers in Physiology. 8: 842. doi:10.3389/fphys.2017.00842. ISSN 1664-042X. PMC 5673639. PMID 29163191.
  9. ^ Stawski, Clare; Geiser, Fritz (2010-01-01). "Fat and fed: frequent use of summer torpor in a subtropical bat". Naturwissenschaften. 97 (1): 29–35. doi:10.1007/s00114-009-0606-x. ISSN 0028-1042. PMID 19756460.
  10. ^ Warnecke, Lisa; Turner, James M.; Geiser, Fritz (2008-01-01). "Torpor and basking in a small arid zone marsupial". Naturwissenschaften. 95 (1): 73–78. doi:10.1007/s00114-007-0293-4. ISSN 0028-1042. PMID 17684718.
  11. ^ Körtner, Gerhard; Geiser, Fritz (2009). "The key to winter survival: daily torpor in a small arid-zone marsupial". Naturwissenschaften. 96 (4): 525–530. doi:10.1007/s00114-008-0492-7. PMID 19082573.
  12. ^ Batholomew, G. (1982). "Energy Metabolism". Animal Physiology: Principles and Adaptations. Macmillan Publishing Co.
  13. ^ Allaby, Michael (2014). A Dictionary of Zoology. Oxford University Press. p. 963. ISBN 9780199684274.
  14. ^ a b Carpenter, F. Lynn; Hixon, Mark A. (May 1988). "A New Function for Torpor: Fat Conservation in a Wild Migrant Hummingbird". The Condor. 90 (2): 373–378. doi:10.2307/1368565. JSTOR 1368565.
  15. ^ Chaplin, Susan Budd (1974-12-01). "Daily energetics of the Black-capped Chickadee,Parus atricapillus, in winter". Journal of Comparative Physiology. 89 (4): 321–330. doi:10.1007/BF00695350. ISSN 0340-7594.
  16. ^ a b c McAllan, B. M.; Geiser, Fritz (2014-09-01). "Torpor during Reproduction in Mammals and Birds: Dealing with an Energetic Conundrum". Integrative and Comparative Biology. 54 (3): 516–532. doi:10.1093/icb/icu093. ISSN 1540-7063. PMID 24973362.
  17. ^ Stawski, Clare; Turbill, Christopher; Geiser, Fritz (2009-05-01). "Hibernation by a free-ranging subtropical bat (Nyctophilus bifax)". Journal of Comparative Physiology B. 179 (4): 433–441. doi:10.1007/s00360-008-0328-y. ISSN 0174-1578. PMID 19112568.
  18. ^ a b Geiser, Fritz; Brigham, R. Mark (2012). Living in a Seasonal World. pp. 109–121. doi:10.1007/978-3-642-28678-0_10. ISBN 978-3-642-28677-3.
  19. ^ a b Levy, Ofir; Dayan, Tamar; Kronfeld-Schor, Noga (2011-09-01). "Interspecific Competition and Torpor in Golden Spiny Mice: Two Sides of the Energy-Acquisition Coin". Integrative and Comparative Biology. 51 (3): 441–448. doi:10.1093/icb/icr071. ISSN 1540-7063. PMID 21719432.
  20. ^ Lourenço, Sofia; Palmeirim, Jorge Mestre (2008-12-01). "Which factors regulate the reproduction of ectoparasites of temperate-zone cave-dwelling bats?". Parasitology Research. 104 (1): 127–34. doi:10.1007/s00436-008-1170-6. ISSN 0932-0113. PMID 18779978.
  21. ^ Hall, Loura (19 July 2013). "Torpor Inducing Transfer Habitat For Human Stasis To Mars". NASA. Retrieved 20 March 2018.

Antechinus /æntɪˈkaɪnəs/ ('ant-echinus') is a genus of small dasyurid marsupial endemic to Australia. They resemble mice with the bristly fur of shrews. They are sometimes also called broad-footed marsupial mice, pouched mice, route rat and/or Antechinus shrews. However, these common names are considered either regional or archaic and the modern common name for the animals is Antechinus.

Antechinus have short fur and are generally greyish or brownish in colour, this varies with species. The fur is dense and generally soft. Their tails are thin and tapering and range from slightly shorter to slightly longer than body length. Their heads are conical in shape and ears are small to medium in size. Some species have a relatively long, narrow snout that gives them a shrew like appearance. Species vary from 12–31cm in length and weigh 16–170 g when fully grown. A. agilis is the smallest known species, and A. swainsonii the largest.

Sexual dimorphism occurs in most species for both weight and skeletal measurements, with males being typically larger and heavier.

Most species nest communally in tree-hollows. They primarily inhabit all forests, woodlands and rainforest as well as heaths and grasslands in some species. The majority of Antechinus species are located on the eastern coast of Australia along the Great Dividing Range. There is a population of A. flavipes in south west Western Australia. A. bellus lives in northern Australia around the Gulf of Carpentaria.


Bats are mammals of the order Chiroptera; with their forelimbs adapted as wings, they are the only mammals naturally capable of true and sustained flight. Bats are more manoeuvrable than birds, flying with their very long spread-out digits covered with a thin membrane or patagium. The smallest bat, and arguably the smallest extant mammal, is Kitti's hog-nosed bat, which is 29–34 mm (1.14–1.34 in) in length, 15 cm (5.91 in) across the wings and 2–2.6 g (0.07–0.09 oz) in mass. The largest bats are the flying foxes and the giant golden-crowned flying fox, Acerodon jubatus, which can weigh 1.6 kg (4 lb) and have a wingspan of 1.7 m (5 ft 7 in).

The second largest order of mammals, bats comprise about 20% of all classified mammal species worldwide, with over 1,200 species. These were traditionally divided into two suborders: the largely fruit-eating megabats, and the echolocating microbats. But more recent evidence has supported dividing the order into Yinpterochiroptera and Yangochiroptera, with megabats as members of the former along with several species of microbats. Many bats are insectivores, and most of the rest are frugivores (fruit-eaters). A few species feed on animals other than insects; for example, the vampire bats feed on blood. Most bats are nocturnal, and many roost in caves or other refuges; it is uncertain whether bats have these behaviours to escape predators. Bats are present throughout the world, with the exception of extremely cold regions. They are important in their ecosystems for pollinating flowers and dispersing seeds; many tropical plants depend entirely on bats for these services.

Bats provide humans with some benefits, at the cost of some threats. Bat dung has been mined as guano from caves and used as fertiliser. Bats consume insect pests, reducing the need for pesticides. They are sometimes numerous enough to serve as tourist attractions, and are used as food across Asia and the Pacific Rim. They are natural reservoirs of many pathogens, such as rabies; and since they are highly mobile, social, and long-lived, they can readily spread disease. In many cultures, bats are popularly associated with darkness, malevolence, witchcraft, vampires, and death.

Common poorwill

The common poorwill (Phalaenoptilus nuttallii) is a nocturnal bird of the family Caprimulgidae, the nightjars. It is found from British Columbia and southeastern Alberta, through the western United States to northern Mexico. The bird's habitat is dry, open areas with grasses or shrubs, and even stony desert slopes with very little vegetation.

Many northern birds migrate to winter within the breeding range in central and western Mexico, though some remain further north. Remarkably, the common poorwill is the only bird known to go into torpor for extended periods (weeks to months). This happens on the southern edge of its range in the United States, where it spends much of the winter inactive, concealed in piles of rocks. Such an extended period of torpor is close to a state of hibernation and is not known among other birds.

Costa's hummingbird

Costa's hummingbird (Calypte costae) is a species of hummingbird.

Evening in Torpor

Evening in Torpor was a student-project that Natalie Merchant and Rob Buck from the band 10,000 Maniacs were involved with around the time that 10,000 Maniacs was beginning. All of the songs were written by Albert Garzon. Natalie contributed vocals to "Daffodils," "Mother's Family Ring," "Crumble Down," and "Bathroom Tile Dance," while Rob contributed guitar to "Rectangles," "Daffodils," "Mother's Family Ring," The Playground," Crumble Down," and "Bathroom Tile Dance." The other tracks on the album ("les Cendriers" and "Defense Rap Trip") included no future Maniacs. The song "les Cendriers," which translates from French as "ashtrays" is the only reference to the name of the makeshift band.

The record was released by Community 3, or simply Comm3, in 1988 and taken off the market under a paid agreement with 10,000 Maniacs.

False antechinus

The genus Pseudantechinus are members of the order Dasyuromorphia. They are often called false antechinuses, although this genus includes the sandstone dibbler, which was previously assigned to a different genus.

The species of this genus are as follows:

Sandstone dibbler, Pseudantechinus bilarni

Fat-tailed false antechinus, Pseudantechinus macdonnellensis

Alexandria false antechinus, Pseudantechinus mimulus

Ningbing false antechinus, Pseudantechinus ningbing

Rory Cooper's false antechinus, Pseudantechinus roryi

Woolley's false antechinus, Pseudantechinus woolleyae

Fat-tailed dunnart

The fat-tailed dunnart (Sminthopsis crassicaudata) is a species of mouse-like marsupial of the Dasyuridae, the family that includes the little red kaluta, quolls, and the Tasmanian devil. It has an average body length of 60–90 millimeters (2.4–3.5 in) with a tail of 45–70 millimeters (1.8–2.8 in). Ear length is 14–16 millimeters (0.55–0.63 in). One of the smallest carnivorous marsupials, its weight varies between 10–20 grams (0.35–0.71 oz). The tail becomes fat a few mm from the proximal end and remains so right up to the tip. They are eaten by many things, including foxes and cats, as well as other feral animals that live among its environment.

Fat-tailed false antechinus

The fat-tailed false antechinus (Pseudantechinus macdonnellensis), also called the fat-tailed pseudantechinus and red-eared antechinus, is a member of the order Dasyuromorphia. It is an inhabitant of western and central Australia.

Five hindrances

In the Buddhist tradition, the five hindrances (Sanskrit: पञ्च निवरण pañca nivāraṇa; Pali: पञ्च नीवरणानि pañca nīvaraṇāni) are identified as mental factors that hinder progress in meditation and in our daily lives. In the Theravada tradition, these factors are identified specifically as obstacles to the jhānas (stages of concentration) within meditation practice. Within the Mahayana tradition, the five hindrances are identified as obstacles to samatha (tranquility) meditation. Contemporary Insight Meditation teachers identify the five hindrances as obstacles to mindfulness meditation.

The five hindrances are:

Sensory desire (kāmacchanda): the particular type of wanting that seeks for happiness through the five senses of sight, sound, smell, taste and physical feeling.

Ill-will (vyāpāda; also spelled byāpāda): all kinds of thought related to wanting to reject; feelings of hostility, resentment, hatred and bitterness.

Sloth-and-torpor (thīna-middha): heaviness of body and dullness of mind which drag one down into disabling inertia and thick depression.

Restlessness-and-worry (uddhacca-kukkucca): the inability to calm the mind.

Doubt (vicikicchā): lack of conviction or trust.

Goodman's mouse lemur

Goodman's mouse lemur (Microcebus lehilahytsara) is a species of mouse lemur from the region near Andasibe in eastern Madagascar.The species is named in honor of primatologist Steven M. Goodman. "Lehilahytsara" is a combination of the Malagasy words which mean "good" and "man". The finding was presented August 10, 2005, along with the discovery of the northern giant mouse lemur (Mirza zaza) as a separate species.In 2005, Goodman was awarded a MacArthur Fellowship for his discovery and further research in Madagascar.

Gray mouse lemur

The gray mouse lemur (Microcebus murinus), grey mouse lemur or lesser mouse lemur, is a small lemur, a type of strepsirrhine primate, found only on the island of Madagascar. Weighing 58 to 67 grams (2.0 to 2.4 oz), it is the largest of the mouse lemurs (genus Microcebus), a group that includes the smallest primates in the world. The species is named for its mouse-like size and coloration and is known locally (in Malagasy) as tsidy, koitsiky, titilivaha, pondiky, and vakiandry. The gray mouse lemur and all other mouse lemurs are considered cryptic species, as they are nearly indistinguishable from each other by appearance. For this reason, the gray mouse lemur was considered the only mouse lemur species for decades until more recent studies began to distinguish between the species.

Like all mouse lemurs, this species is nocturnal and arboreal. It is very active, and though it forages alone, groups of males and females form sleeping groups and share tree holes during the day. It exhibits a form of dormancy called torpor during the cool, dry winter months, and in some cases undergoes seasonal torpor (or hibernation), which is unusual for primates. The gray mouse lemur can be found in several types of forest throughout western and southern Madagascar. Its diet consists primarily of fruit, insects, flowers, and nectar. In the wild, its natural predators include owls, snakes, and endemic mammalian predators. Predation pressure is higher for this species than among any other primate species, with one out of four individuals taken by a predator each year. This is counterbalanced by its high reproductive rate. Breeding is seasonal, and distinct vocalizations are used to prevent hybridization with species that overlap its range. Gestation lasts approximately 60 days, and typically two young are born. The offspring are usually independent in two months, and can reproduce after one year. The gray mouse lemur has a reproductive lifespan of five years, although captive individuals have been reported to live up to 15 years.

Although threatened by deforestation, habitat degradation, and live capture for the pet trade, it is considered one of Madagascar's most abundant small native mammals. It can tolerate moderate food shortages by experiencing daily torpor to conserve energy, but extended food shortages due to climate change may pose a significant risk to the species.


Heterothermy or heterothermia (from Greek ἕτερος heteros "other" and θέρμη thermē "heat") is a physiological term for animals that vary between self-regulating their body temperature, and allowing the surrounding environment to affect it. In other words, they exhibit characteristics of both poikilothermy and homeothermy.


Hibernation is a state of inactivity and metabolic depression in endotherms. Hibernation refers to a season of heterothermy characterized by low body temperature, slow breathing and heart rate, and low metabolic rate. It is most commonly observed during the winter months. Although traditionally reserved for "deep" hibernators such as rodents, the term has been redefined to include animals such as bears and is now applied based on active metabolic suppression rather than any absolute decline in body temperature. Many experts believe that the processes of daily torpor and hibernation form a continuum and utilize similar mechanisms. The equivalent during the summer months is aestivation.

Often associated with low temperatures, hibernation functions to conserve energy when sufficient food is unavailable. To achieve this energy saving, an endothermic animal decreases its metabolic rate and thereby its body temperature. Hibernation may last days, weeks, or months depending on the species, ambient temperature, time of year, and the individual's body condition. Before entering hibernation, animals need to store enough energy to last through the duration of their dormant period, possibly as long as the entire winter. Larger species become hyperphagic, eating a large amount of food and storing the energy in fat deposits. In many small species, food caching replaces eating and becoming fat.Some species of mammals hibernate while gestating young, which are born either while the mother hibernates or shortly afterwards. For example, female polar bears go into hibernation during the cold winter months in order to give birth to their offspring. The pregnant mothers significantly increase their body mass prior to hibernation, and this increase is further reflected in the weight of the offspring. The fat accumulation enables them to provide a sufficiently warm and nurturing environment for their newborns. During hibernation, they subsequently lose 15–27% of their pre-hibernation weight by using their stored fats for energy.True hibernation is restricted to endotherms; ectotherms by definition cannot hibernate because they cannot actively down-regulate their body temperature or their metabolic rate. Still, many ectothermic animals undergo periods of dormancy which are sometimes confused with hibernation. Some reptile species are said to brumate, but possible similarities between brumation and hibernation are not firmly established. Many insects, such as the wasp Polistes exclamans, exhibit periods of dormancy which have often been referred to as hibernation, despite their ectothermy.


Hummingbirds are birds native to the Americas and constitute the biological family Trochilidae. They are the smallest of birds, most species measuring 7.5–13 cm (3–5 in) in length. The smallest extant bird species is the 5 cm (2.0 in) bee hummingbird, which weighs less than 2.0 g (0.07 oz).

They are known as hummingbirds because of the humming sound created by their beating wings which flap at high frequencies audible to humans. They hover in mid-air at rapid wing-flapping rates, which vary from around 12 beats per second in the largest species, to in excess of 80 in some of the smallest. Of those species that have been measured in wind tunnels, their top speed exceeds 15 m/s (54 km/h; 34 mph) and some species can dive at speeds in excess of 22 m/s (79 km/h; 49 mph).Hummingbirds have the greatest mass-specific metabolic rate of any homeothermic animal. To conserve energy when food is scarce, and nightly when not foraging, they can go into torpor, a state similar to hibernation, slowing metabolic rate to 1/15th of its normal rate.


The kultarr (Antechinomys laniger) (also called the "jerboa-marsupial") is a small insectivorous nocturnal marsupial inhabiting the arid interior of Australia. Preferred habitat includes stony deserts, shrubland, woodland, grassland and open plains. The kultarr has a range of adaptations to help cope with Australia’s harsh arid environment including torpor similar to hibernation that helps conserve energy The species has declined across its former range since European settlement due to changes in land management practices and introduced predators.

Sugar glider

The sugar glider (Petaurus breviceps) is a small, omnivorous, arboreal, and nocturnal gliding possum belonging to the marsupial infraclass. The common name refers to its preference for sugary foods like sap and nectar and its ability to glide through the air, much like a flying squirrel. They have very similar habits and appearance to the flying squirrel, despite not being closely related—an example of convergent evolution. The scientific name, Petaurus breviceps, translates from Latin as "short-headed rope-dancer", a reference to their canopy acrobatics.The sugar glider is characterised by its gliding membrane, known as the patagium, which extends from its forelegs to its hindlegs, one on each side of its body. Gliding serves as an efficient means of reaching food and evading predators. The animal is covered in soft, pale grey to light brown fur which is countershaded, being lighter in colour on its underside.

The sugar glider is endemic to parts of mainland Australia, New Guinea and certain Indonesian islands; and it was introduced to Tasmania, probably in the 1830s. It is a popular exotic pet but is prohibited in some regions, including parts of Australia and the United States.

Tawny frogmouth

The tawny frogmouth (Podargus strigoides) is a species of frogmouth native to and found throughout the Australian mainland and Tasmania. It is a big-headed, stocky bird, often mistaken for an owl due to its nocturnal habits and similar colouring, and is sometimes incorrectly referred to as "mopoke", a common name for the Australian boobook, whose call is often confused with the tawny frogmouth's.


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 as its own body temperature, thus avoiding the need for internal thermoregulation. The internal thermoregulation process is one aspect of homeostasis: a state of dynamic stability in an organism's internal conditions, maintained far from thermal equilibrium with its environment (the study of such processes in zoology has been called physiological ecology). If the body is unable to maintain a normal temperature and it increases significantly above normal, a condition known as hyperthermia occurs. For humans, this occurs when the body is exposed to constant temperatures of approximately 55 °C (131 °F), and with prolonged exposure (longer than a few hours) at this temperature and up to around 75 °C (167 °F) death is almost inevitable. Humans may also experience lethal hyperthermia when the wet bulb temperature is sustained above 35 °C (95 °F) for six hours. The opposite condition, when body temperature decreases below normal levels, is known as hypothermia. It results when the homeostatic control mechanisms of heat within the body malfunction, causing the body to lose heat faster than producing it. Normal body temperature is around 37 °C (99 °F), and hypothermia sets in when the core body temperature gets lower than 35 °C (95 °F). Usually caused by prolonged exposure to cold temperatures, hypothermia is usually treated by methods that attempt to raise the body temperature back to a normal range.It was not until the introduction of thermometers that any exact data on the temperature of animals could be obtained. It was then found that local differences were present, since heat production and heat loss vary considerably in different parts of the body, although the circulation of the blood tends to bring about a mean temperature of the internal parts. Hence it is important to identify the parts of the body that most closely reflect the temperature of the internal organs. Also, for such results to be comparable, the measurements must be conducted under comparable conditions. The rectum has traditionally been considered to reflect most accurately the temperature of internal parts, or in some cases of sex or species, the vagina, uterus or bladder.Occasionally the temperature of the urine as it leaves the urethra may be of use in measuring body temperature. More often the temperature is taken in the mouth, axilla, ear or groin.Some animals undergo one of various forms of dormancy where the thermoregulation process temporarily allows the body temperature to drop, thereby conserving energy. Examples include hibernating bears and torpor in bats.


Thīna (Sanskrit, Pāli: थीन thīna) is a Buddhist term that is translated as "sloth". Thīna is defined as sluggishness or dullness of mind, characterized by a lack of driving power. In the Theravada tradition, thīna is said to occur in conjunction with middha (torpor), which is defined as a morbid state that is characterized by unwieldiness, lack of energy, and opposition to wholesome activity. The two mental factors in conjunction are expressed as thīna-middha (sloth-torpor).

Thīna is mentioned in the Pali canon as:

One of the five hindrances to meditation practice (in combination with middha, i.e. as sloth-torpor)

One of the fourteen unwholesome mental factors within the Theravada Abhidharma teachings

Closely related to the Sanskrit term kausīdya (spiritual sloth), that is identified as one of the twenty secondary unwholesome factors within the Mahayana Abhidharma teachings


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