Here's a little something I wrote up years ago to clear up the issue for another forum:
Quiescent States in Vertebrates 101
Terminology
Sleep: The state of sleep as described in mammals is characterized by recurrent spontaneous bouts of inactivity with concomitant elevated thresholds of sensory response and greatly reduced cognitive function or unconsciousness (McGinty & Beahm, 1984). Sleep is differentiated from other states of unconsciousness, such as coma, by being readily reversible. Electroencephalographic (EEG) studies show mammals and birds possess two distinct phases of sleep, slow wave sleep (SWS) and paradoxical sleep (PS). Slow wave sleep, also known as non-rapid-eye-movement (NREM) sleep, is associated with synchronized cortical EEG activity of high amplitude and low frequency with occasional high frequency spikes while paradoxical sleep (PS), also known as rapid-eye-movement (REM) or activated sleep, is associated with desynchronized EEG activity of low amplitude very similar to that seen in the awake state (Steriade, et al., 1993). In endotherms, sleep is associated with a progressive decline in brain temperature (Tbr) and metabolism as sleep duration increases (for review, see Heller & Glotzbach, 1977). Sleep also has behavioural correlates such as specific sleep sites or postures and a distinct latency of behavioural response to stimulation (for review, see McGinty & Beahm, 1984).
Many of the criteria that have been used to identify sleep states in mammals and birds do not describe the sleeping condition seen in less encephalized animals such as reptiles. Attempts to quantify reptilian cortical EEG activity using mammalian characteristics (e.g. Huntley, et al., 1977; Meglasson & Huggins, 1979; Huntley & Cohen, 1980) have been relatively unsuccessful. While spike EEG activity homologous with that recorded from mammalian limbic systems does arise from the forebrain of reptiles during sleep (Diaz, et al., 1973; Hartse, et al., 1979), and is absent in both taxa during wakefulness, sleep states in reptiles with EEG profiles comparable to those seen in mammals are usually no longer than a few seconds occurring in bouts of "behavioural sleep" lasting several hours (Huntley & Cohen, 1980; K. Rogers & W.K. Milsom, unpublished data). Sleep in reptiles therefore is usually quantified based on behavioural criteria which include posture, closed eyelids, increased latency of responses to stimulation, and reduced but regular ventilation and cardiac frequencies (Flanigan, 1973, 1974; Flanigan, et al., 1973, 1974; Huntley, et al., 1977; Huntley & Cohen, 1980).
Torpor: Torpor was first used to describe the phenomenon during which many endotherms allow their body temperatures to drop below levels considered normal for sleep, but not as low as the levels typically observed in hibernation (Morrison & Ryser, 1959; Tucker, 1962; MacMillen, 1964). As such, torpor usually involves a drop in Tb greater than 5°C and as much as 15°-20°C below normal, a reduction in resting metabolic rate by more than 25%, and usually occurs on a daily basis during the normal quiescent period of sleep. It may, however, extend over several days (Heller, et al., 1978; Hudson & Scott, 1979; Körtner & Geiser, 2000).
The term torpor has never been defined clearly as it pertains to ectotherms, and this has lead to its free use to describe nearly any quiescent state. There are researchers that subscribe to the idea that torporis simply a function of reduced body temperature (e.g. Hock, 1958) and others that use torpor and hibernation interchangeably to denote the winter quiescent period (e.g. Binyon & Twigg, 1965; Ultsch, 1989). Most researchers have adopted the term in the mammalian sense to describe a profound daily reduction in metabolism due to declining ambient temperature during the inactive phase (e.g. Potter & Glass, 1931; Holzapfel, 1937; Willis, et al., 1956). As such, it involves a daily reduction in metabolism to a level below that predicted by changes in body temperature alone, is readily reversible and involves a greater latency of responsiveness to stimulation than that associated with sleep.
Hibernation: In general usage, to hibernate is to spend the winter in an inactive, sleep-like state and occurs in practically every phylum. For endothermic vertebrates it generally involves a seasonal reduction in body temperature to levels within a few degrees of ambient temperature (Ta). Hibernation occurs in bouts that last for periods of days, weeks, or even months and that are interspersed by short periods of arousal during which the animals spontaneously rewarm (Körtner & Geiser, 2000) and may undertake moderate activity. The duration of these bouts varies from species to species as well as with ambient temperature and position in the winter season (early, mid, late) within species (Twente & Twente, 1965; Twente, et al., 1977; Kenagy, 1981; French 1982; Wilz & Heldmaier, 2000).
Hibernation in ectothermic vertebrates, unfortunately, is not well defined. There do appear, however, to be some common physiological phenomena correlated with hibernation observed in ectotherms and in particular, in reptiles (Bennett & Dawson, 1976.) Preparation for entrance into hibernation begins well before the winter season with many reptiles spontaneously initiating fasting in the fall (Cagle, 1950; Hernandez & Coulson, 1952; Musacchia & Sievers, 1956; Hutton & Goodnight, 1957; Coulson & Hernandez, 1964; Mayhew, 1965; Chabreck & Joanen, 1969; Fitch & von Achen, 1977; Abe, 1983; de Andrade & Abe, 1999). It also involves what has been termed by some as "inverse acclimatization" (Mayhew, 1965; Jacobson & Whitford, 1970; Gatten, 1978; Patterson & Davies, 1978; Johansen & Lykkeboe, 1979; Abe, 1983). Many reptiles increase their metabolic rate to compensate for cold temperatures (Roberts, 1968; Tinkle and Hadley, 1973; Dutton and Fitzpatrick, 1975; Ruby, 1977) and some develop an insensitivity of metabolic rate to changes in body temperature (Gelineo, 1967). This acclimation usually occurs in reptiles inhabiting regions with little or moderate seasonal variation and allows them to continue to function normally at lower temperatures. Inverse acclimatization, or hibernation, on the other hand occurs in reptiles that inhabit regions with more pronounced seasonality and involves active metabolic suppression.
Dormancy: There appears to be some confusion in the literature surrounding the terms dormancy and hibernation, especially when used with respect to reptiles. Many authors interchange the terms and give them equal meaning; others use hibernation to denote a specific type of dormancy (e.g. Mayhew, 1965; Gregory, 1982). Hibernation in common usage refers to winter inactivity while dormancy has no similar temporal qualification. For the purpose of this dissertation, dormancy is used as a general reference to any quiescent state involving reduced metabolic rate, including sleep, torpor, aestivation (a quiescent state associated with excessive heat) and hibernation.
Brumation: Mayhew (1965) proposed the term brumation to define inactivity and physiological changes identified with winter dormancy in ectotherms that occur independent of body temperature, to differentiate it from simple cold-induced inactivity, and hibernation seen in mammals. While some authors have adopted the term (e.g. Gaffney and Fitzpatrick, 1973; Huey & Pianka, 1977; Hutchinson, 1979; Rismiller & Heldmaier, 1982), it has not achieved wide acceptance academically, and most authors overlook the distinction of the state being temperature independent.
Synopsis
In plain english, hibernation is well definied in mammals, and the criteria used to define it does not exactly match what we would observe in reptiles. However, we can draw certain analogies to come up with a reptilian "version" of hibernation. For a state to be called "hibernation" in reptiles (and to differentiate it from sleep or cold induced "coma"), it would have to have seasonal reference (winter), inactivity (sort of sleeping) and involve a concomitant supressed metabolism (that is, metabolism that is even lower than what would be predicted by temperature effects alone - or in other words, their metabolism would be independent of temperature). We therefore see that the phenomenon defined by Mayhew as "brumation" is EXACTLY what we would describe as "hibernation" in a reptile.
As seen in some of the posts (and elsewhere), many want to draw a distinction by saying "hibernation" does not have arousals whereas "brumation" has some activity. By looking at the scientific literature, we see that "hibernation" in mammals does indeed involve arousals. People assume that in reptiles this does not occur, but what they forget is that this is an assumption only. Recent studies with modern technological advancements has shown us that our previously held beliefs of reptiles being inactive during hibernation are false. Like mammals, reptiles too will arouse periodically during "hibernation". In temperate areas, we just do not naturally observe this because if the animals left their hibernacula they would die from exposure. They are, however, active within their burrows (or in cases like turtles/terrapins, have been recorded moving around under the ice of frozen bodies of water).
About the only distinction between "hibernation" in mammals and "hibernation/brumation" in reptiles is seen in the energy substrate used during the dormancy. Mammals choose lipids for their energy, whereas reptiles retain storage of the lipids as the lipids become more important for post-hibernation purposes (primarily for deposition in macrolecithal eggs by females, courtship and competition by males). Some studies have indicated reptiles use glycogen, while there are other observations that indicate they may utilize protein energy substrates.
Boiled down, brumation IS hibernation in reptiles. There is still debate amongst physiologists in regards to this topic, and that is whether sleep, torpor and hibernation/brumation are distinctly separate physiological states, or merely points along a continuum. The distinct states argument hinges upon the definitions being the "end all and be all" of the argument (ie. beings as torpor is a daily pattern while hibernation is a seasonal pattern, they are distinct) while the continuum argument points out the many many examples of phenomena that don't tightly fit one definition or another and lie somewhere inbetween. My own research in reptiles has me in the continuum group.
Abe, A.S., 1983. Observations on dormancy in tegu lizards – Tupinambis teguixin (Reptilia, Teiidae). Naturalia 8: 235-239.
Abe, A.S., 1995. Estivation in South American amphibians and reptiles. Brazilian Journal of Medicine and Biology Research 28: 1241-1247.
Bennett, A.F. and W.R. Dawson, 1976. Metabolism, Chapter 3. Pp 127-223 in Biology of the Reptilia, Volume 5; Physiology A. C. Gans and W.R. Dawson (eds.). Academic Press, London.
Binyon, E.J., and G.I. Twigg, 1965. Seasonal changes in the blood and thyroid of the grass snake, Natrix natrix. Nature 207:779-780.
Cagle, F.R., 1950. The life history of the slider turtle, Pseudemys scripta troostii (Holbrook). Ecology Monographs 20: 31-54.
Chabreck, R.H., and T. Joanen, 1979. Growth rates of American alligators in Louisiana. Herpetologica 35: 51-57.
Coulson, R.A., and T. Hernandez, 1964. Biochemistry of the Alligator: A study of Metabolism in Slow Motion. Louisiana State University Press, Baton Rouge, Louisiana.
de Andrade, D.V. and A.S. Abe, 1999. Gas exchange and ventilation during dormancy in the tegu lizard Tupinambis merianae. Journal of Experimental Biology 202: 3677-3685.
Diaz, J., M. Fairbanks and J. McGinty, 1973. Amygdala spiking during slow wave sleep and rapid eye movement. Sleep Research 2: 23.
Fitch, H.S., and P.L. von Achen, 1977. Spatial relationships and seasonality in the skinks Eumeces fasciatus and Scincella laterale, in northeastern Kansas. Herpetologica 33: 303-313.
Flanigan, W.F., 1974. Sleep and Wakefulness in chelonian reptiles. II. The red-footed tortoise, Geochelone carbonaria. Archives Italiennes de Biologie 112: 253-275.
Flanigan, W.F. Jr., 1973. Sleep and wakefulness in iguanid lizards, Ctenosaura pectinata and Iguana iguana. Brain, Behavior & Evolution 8: 401-436.
Flanigan, W.F. Jr., C.P. Knight, K.M. Hartse and A. Rechtschaffen, 1974. Sleep and wakefulness in chelonian reptiles. I. The box turtle, Terrapene carolina. Archives Italiennes de Biologie 112: 227-252.
French, A.R., 1982. Effects of temperature on the duration of arousal episodes during hibernation. Journal of Applied Physiology 52: 216-220.
Gaffney, F.G. and L.C. Fitzpatrick, 1973. Energetics and lipid cycles in the lizard Cnemidophorus tigris. Copeia 1973: 446-452.
Gatten, R.E., Jr., 1978. Aerobic metabolism in snapping turtles, Chelydra serpentina, after thermal acclimation. Comparative Biochemistry & Physiology A 61: 325-337.
Gelineo, S., 1967. Oxygen consumption in lizards on the way to winter sleep. Bulletin of the Academy of Serbe Sciences 39: 51-57.
Gregory, P.T., 1982. Reptilian Hibernation, Chapter 2. Pp 53-154 in Biology of the Reptilia, Volume 13; Physiology D, Physiological Ecology. C. Gans and F.H. Pough (eds.). Academic Press, London.
Hartse, K.M., S.F. Eisenhart, B.M. Bergmann, and A. Rechtschaffen, 1979. Ventral hippocampus spikes during sleep, wakefulness, and arousal in the cat. Sleep 1: 231-246.
Heller, H.C. and S.F. Glotzbach, 1977. Thermoregulation During Sleep and Hibernation. Pp 147-188 in International Review of Physiology: Environmental Physiology II, Volume 15. D. Robertshaw (ed.). University Park Press, Baltimore.
Heller, H.C., G.L. Florant, S.F. Glotzbach, J.M. Walker and R.J. Berger, 1978. Sleep and Torpor – Homologous Adaptations for Energy Conservation. Pp 269-296 in Dormancy and Developmental Arrest. Experimental Analysis in Plants and Animals. M.E. Clutter (ed.). Academic Press, New York.
Hernandez, T., and R.A. Coulson, 1952. Hibernation in the alligator. Proceedings of the Society of Experimental Biology and Medicine 79: 145-149.
Hock, R.J.,1958. Hibernation. Pp 61-133 in Josiah Macy Foundation Fifth Conference on Cold Injury.
Holzapfel, R.A., 1937. The cyclic character of hibernation in frogs. Quarterly Review of Biology 12: 65-84.
Hudson, J.W., and I.M. Scott, 1979. Daily torpor in the laboratory mouse, Mus musculus var albino. Physiological Zoölogy 52: 205-218.
Huntley, A.C., J.K. Friedmann, and H.B. Cohen, 1977. Sleep in an iguanid lizard, Dipsosaurus dorsalis. Sleep Research 6:104.
Huntley, A.C., and H.B. Cohen, 1980. Further comments on "sleep" in the desert iguana, Dipsosaurus dorsalis. Sleep Research 9: 111.
Hutton, K.E., and C.J. Goodnight, 1957. Variations in blood chemistry of turtles under active and hibernating conditions. Physiological Zoölogy 30: 198-207.
Jacobson, E.R., and W.G. Whitford, 1970. The effect of acclimation on the physiological responses to temperature in the snakes Thamnophis proximus and Natrix rhombifera. Comparative Biochemistry and Physiology 35: 439-449.
Kenagy, G.J., 1981. Effects of day length, temperature and endogenous control on annual rhythms of reproduction and hibernation in chipmunks (Eutamias spp.). Journal of Comparative Physiology 141: 369-378.
Körtner, G., and F.Geiser, 2000. The temporal organization of daily torpor and hibernation: circadian and circannual rhythms. Chronobiology International 17: 103-128.
MacMillen, R.E., 1964. Aestivation in the cactus mouse and its significance as a water conserving mechanism. American Zoölogist 4: 304.
Mayhew, W.W., 1965. Hibernation in the horned lizard, Phrynosoma m’calli. Comparative Biochemistry & Physiology 16: 103-119.
McGinty, D.J. and E.K. Beahm, 1984. Neurobiology of Sleep. Pp 1-89 in Sleep and Breathing, Volume 21 Lung Biology in Health and Disease. C. Lenfant, N.A. Saunders and C.E. Sullivan (eds.). Marcel Dekker, Inc., New York.
Meglasson, M.D., and S.E. Huggins, 1979. Sleep in a crocodilian, Caiman sclerops. Comparative Biochemistry and Physiology A 63: 561-567.
Morrison, P., and F.A. Ryser, 1959. Body temperature in the white-footed mouse, Peromyscus leucopus noveboracensis. Physiological Zoölogy 32: 90-103.
Musacchia, X.J., and M.L. Sievers, 1956. Effects of induced cold torpor on blood of Chrysemys picta. American Journal of Physiology 187: 99-102.
Potter, G.E., and H.B. Glass, 1931. A study of respiration in hibernating horned lizards, Phrynosoma cornutum. Copeia 1931: 128-131.
Rismiller, P.D. and G. Heldmaier, 1982. The effect of photoperiod on temperature selection in the European green lizard, Lacerta viridis. Oecologia 53: 222-226.
Rismiller, P.D., and M.W. McKelvey, 2000. Spontaneous arousal in reptiles? Body temperature ecology of Rosenberg’s Goanna, Varanus rosenbergi. Pp 57-64 in Life in the cold. G. Heldmaier and M. Klingenspor (eds.). Springer-Verlag, Berlin, Heidelberg, New York.
Steriade, M., D.A. McCormick and T.J. Sejnowski, 1993. Thalamocortical oscillations in the sleep and aroused brain. Science 262: 679-685.
Tucker, V., 1962. Diurnal torpidity in the California pocket mouse. Science 136: 380-381.
Twente, J.W., and J.A. Twente, 1965. Regulation of hibernating periods by temperature. Proceedings of the National Academy of Sciences, USA 54: 1058-1061.
Twente, J.W., and J.A. Twente, 1967. Seasonal variation in the hibernating behaviour of Citellus lateralis. Pp 47-63 in Mammalian Hibernation III. Fisher, K.C., A.R. Dawe, C.P. Lyman, E. Schöbaum and F.E. South, Jr. (eds.). American Elsevier Publishing Company, Inc., New York.
Twente, J.W., J.A. Twente and R.M. Moy, 1977. Regulation of arousal from hibernation by temperature in three species of Citellus. Journal of Applied Physiology 42: 191-195.
Ultsch, G.R., 1989. Ecology and physiology of hibernation and overwintering among freshwater fishes, turtles, and snakes. Biology Review 64: 435-516.
Willis, Y.L., D.L. Moyle and T.S. Baskett, 1956. Emergence, breeding, hibernation, movements, and transformation of the bullfrog, Rana catesbeiana, in Missouri. Copeia 1956: 30-41.
Quiescent States in Vertebrates 101
Terminology
Sleep: The state of sleep as described in mammals is characterized by recurrent spontaneous bouts of inactivity with concomitant elevated thresholds of sensory response and greatly reduced cognitive function or unconsciousness (McGinty & Beahm, 1984). Sleep is differentiated from other states of unconsciousness, such as coma, by being readily reversible. Electroencephalographic (EEG) studies show mammals and birds possess two distinct phases of sleep, slow wave sleep (SWS) and paradoxical sleep (PS). Slow wave sleep, also known as non-rapid-eye-movement (NREM) sleep, is associated with synchronized cortical EEG activity of high amplitude and low frequency with occasional high frequency spikes while paradoxical sleep (PS), also known as rapid-eye-movement (REM) or activated sleep, is associated with desynchronized EEG activity of low amplitude very similar to that seen in the awake state (Steriade, et al., 1993). In endotherms, sleep is associated with a progressive decline in brain temperature (Tbr) and metabolism as sleep duration increases (for review, see Heller & Glotzbach, 1977). Sleep also has behavioural correlates such as specific sleep sites or postures and a distinct latency of behavioural response to stimulation (for review, see McGinty & Beahm, 1984).
Many of the criteria that have been used to identify sleep states in mammals and birds do not describe the sleeping condition seen in less encephalized animals such as reptiles. Attempts to quantify reptilian cortical EEG activity using mammalian characteristics (e.g. Huntley, et al., 1977; Meglasson & Huggins, 1979; Huntley & Cohen, 1980) have been relatively unsuccessful. While spike EEG activity homologous with that recorded from mammalian limbic systems does arise from the forebrain of reptiles during sleep (Diaz, et al., 1973; Hartse, et al., 1979), and is absent in both taxa during wakefulness, sleep states in reptiles with EEG profiles comparable to those seen in mammals are usually no longer than a few seconds occurring in bouts of "behavioural sleep" lasting several hours (Huntley & Cohen, 1980; K. Rogers & W.K. Milsom, unpublished data). Sleep in reptiles therefore is usually quantified based on behavioural criteria which include posture, closed eyelids, increased latency of responses to stimulation, and reduced but regular ventilation and cardiac frequencies (Flanigan, 1973, 1974; Flanigan, et al., 1973, 1974; Huntley, et al., 1977; Huntley & Cohen, 1980).
Torpor: Torpor was first used to describe the phenomenon during which many endotherms allow their body temperatures to drop below levels considered normal for sleep, but not as low as the levels typically observed in hibernation (Morrison & Ryser, 1959; Tucker, 1962; MacMillen, 1964). As such, torpor usually involves a drop in Tb greater than 5°C and as much as 15°-20°C below normal, a reduction in resting metabolic rate by more than 25%, and usually occurs on a daily basis during the normal quiescent period of sleep. It may, however, extend over several days (Heller, et al., 1978; Hudson & Scott, 1979; Körtner & Geiser, 2000).
The term torpor has never been defined clearly as it pertains to ectotherms, and this has lead to its free use to describe nearly any quiescent state. There are researchers that subscribe to the idea that torporis simply a function of reduced body temperature (e.g. Hock, 1958) and others that use torpor and hibernation interchangeably to denote the winter quiescent period (e.g. Binyon & Twigg, 1965; Ultsch, 1989). Most researchers have adopted the term in the mammalian sense to describe a profound daily reduction in metabolism due to declining ambient temperature during the inactive phase (e.g. Potter & Glass, 1931; Holzapfel, 1937; Willis, et al., 1956). As such, it involves a daily reduction in metabolism to a level below that predicted by changes in body temperature alone, is readily reversible and involves a greater latency of responsiveness to stimulation than that associated with sleep.
Hibernation: In general usage, to hibernate is to spend the winter in an inactive, sleep-like state and occurs in practically every phylum. For endothermic vertebrates it generally involves a seasonal reduction in body temperature to levels within a few degrees of ambient temperature (Ta). Hibernation occurs in bouts that last for periods of days, weeks, or even months and that are interspersed by short periods of arousal during which the animals spontaneously rewarm (Körtner & Geiser, 2000) and may undertake moderate activity. The duration of these bouts varies from species to species as well as with ambient temperature and position in the winter season (early, mid, late) within species (Twente & Twente, 1965; Twente, et al., 1977; Kenagy, 1981; French 1982; Wilz & Heldmaier, 2000).
Hibernation in ectothermic vertebrates, unfortunately, is not well defined. There do appear, however, to be some common physiological phenomena correlated with hibernation observed in ectotherms and in particular, in reptiles (Bennett & Dawson, 1976.) Preparation for entrance into hibernation begins well before the winter season with many reptiles spontaneously initiating fasting in the fall (Cagle, 1950; Hernandez & Coulson, 1952; Musacchia & Sievers, 1956; Hutton & Goodnight, 1957; Coulson & Hernandez, 1964; Mayhew, 1965; Chabreck & Joanen, 1969; Fitch & von Achen, 1977; Abe, 1983; de Andrade & Abe, 1999). It also involves what has been termed by some as "inverse acclimatization" (Mayhew, 1965; Jacobson & Whitford, 1970; Gatten, 1978; Patterson & Davies, 1978; Johansen & Lykkeboe, 1979; Abe, 1983). Many reptiles increase their metabolic rate to compensate for cold temperatures (Roberts, 1968; Tinkle and Hadley, 1973; Dutton and Fitzpatrick, 1975; Ruby, 1977) and some develop an insensitivity of metabolic rate to changes in body temperature (Gelineo, 1967). This acclimation usually occurs in reptiles inhabiting regions with little or moderate seasonal variation and allows them to continue to function normally at lower temperatures. Inverse acclimatization, or hibernation, on the other hand occurs in reptiles that inhabit regions with more pronounced seasonality and involves active metabolic suppression.
Dormancy: There appears to be some confusion in the literature surrounding the terms dormancy and hibernation, especially when used with respect to reptiles. Many authors interchange the terms and give them equal meaning; others use hibernation to denote a specific type of dormancy (e.g. Mayhew, 1965; Gregory, 1982). Hibernation in common usage refers to winter inactivity while dormancy has no similar temporal qualification. For the purpose of this dissertation, dormancy is used as a general reference to any quiescent state involving reduced metabolic rate, including sleep, torpor, aestivation (a quiescent state associated with excessive heat) and hibernation.
Brumation: Mayhew (1965) proposed the term brumation to define inactivity and physiological changes identified with winter dormancy in ectotherms that occur independent of body temperature, to differentiate it from simple cold-induced inactivity, and hibernation seen in mammals. While some authors have adopted the term (e.g. Gaffney and Fitzpatrick, 1973; Huey & Pianka, 1977; Hutchinson, 1979; Rismiller & Heldmaier, 1982), it has not achieved wide acceptance academically, and most authors overlook the distinction of the state being temperature independent.
Synopsis
In plain english, hibernation is well definied in mammals, and the criteria used to define it does not exactly match what we would observe in reptiles. However, we can draw certain analogies to come up with a reptilian "version" of hibernation. For a state to be called "hibernation" in reptiles (and to differentiate it from sleep or cold induced "coma"), it would have to have seasonal reference (winter), inactivity (sort of sleeping) and involve a concomitant supressed metabolism (that is, metabolism that is even lower than what would be predicted by temperature effects alone - or in other words, their metabolism would be independent of temperature). We therefore see that the phenomenon defined by Mayhew as "brumation" is EXACTLY what we would describe as "hibernation" in a reptile.
As seen in some of the posts (and elsewhere), many want to draw a distinction by saying "hibernation" does not have arousals whereas "brumation" has some activity. By looking at the scientific literature, we see that "hibernation" in mammals does indeed involve arousals. People assume that in reptiles this does not occur, but what they forget is that this is an assumption only. Recent studies with modern technological advancements has shown us that our previously held beliefs of reptiles being inactive during hibernation are false. Like mammals, reptiles too will arouse periodically during "hibernation". In temperate areas, we just do not naturally observe this because if the animals left their hibernacula they would die from exposure. They are, however, active within their burrows (or in cases like turtles/terrapins, have been recorded moving around under the ice of frozen bodies of water).
About the only distinction between "hibernation" in mammals and "hibernation/brumation" in reptiles is seen in the energy substrate used during the dormancy. Mammals choose lipids for their energy, whereas reptiles retain storage of the lipids as the lipids become more important for post-hibernation purposes (primarily for deposition in macrolecithal eggs by females, courtship and competition by males). Some studies have indicated reptiles use glycogen, while there are other observations that indicate they may utilize protein energy substrates.
Boiled down, brumation IS hibernation in reptiles. There is still debate amongst physiologists in regards to this topic, and that is whether sleep, torpor and hibernation/brumation are distinctly separate physiological states, or merely points along a continuum. The distinct states argument hinges upon the definitions being the "end all and be all" of the argument (ie. beings as torpor is a daily pattern while hibernation is a seasonal pattern, they are distinct) while the continuum argument points out the many many examples of phenomena that don't tightly fit one definition or another and lie somewhere inbetween. My own research in reptiles has me in the continuum group.
Abe, A.S., 1983. Observations on dormancy in tegu lizards – Tupinambis teguixin (Reptilia, Teiidae). Naturalia 8: 235-239.
Abe, A.S., 1995. Estivation in South American amphibians and reptiles. Brazilian Journal of Medicine and Biology Research 28: 1241-1247.
Bennett, A.F. and W.R. Dawson, 1976. Metabolism, Chapter 3. Pp 127-223 in Biology of the Reptilia, Volume 5; Physiology A. C. Gans and W.R. Dawson (eds.). Academic Press, London.
Binyon, E.J., and G.I. Twigg, 1965. Seasonal changes in the blood and thyroid of the grass snake, Natrix natrix. Nature 207:779-780.
Cagle, F.R., 1950. The life history of the slider turtle, Pseudemys scripta troostii (Holbrook). Ecology Monographs 20: 31-54.
Chabreck, R.H., and T. Joanen, 1979. Growth rates of American alligators in Louisiana. Herpetologica 35: 51-57.
Coulson, R.A., and T. Hernandez, 1964. Biochemistry of the Alligator: A study of Metabolism in Slow Motion. Louisiana State University Press, Baton Rouge, Louisiana.
de Andrade, D.V. and A.S. Abe, 1999. Gas exchange and ventilation during dormancy in the tegu lizard Tupinambis merianae. Journal of Experimental Biology 202: 3677-3685.
Diaz, J., M. Fairbanks and J. McGinty, 1973. Amygdala spiking during slow wave sleep and rapid eye movement. Sleep Research 2: 23.
Fitch, H.S., and P.L. von Achen, 1977. Spatial relationships and seasonality in the skinks Eumeces fasciatus and Scincella laterale, in northeastern Kansas. Herpetologica 33: 303-313.
Flanigan, W.F., 1974. Sleep and Wakefulness in chelonian reptiles. II. The red-footed tortoise, Geochelone carbonaria. Archives Italiennes de Biologie 112: 253-275.
Flanigan, W.F. Jr., 1973. Sleep and wakefulness in iguanid lizards, Ctenosaura pectinata and Iguana iguana. Brain, Behavior & Evolution 8: 401-436.
Flanigan, W.F. Jr., C.P. Knight, K.M. Hartse and A. Rechtschaffen, 1974. Sleep and wakefulness in chelonian reptiles. I. The box turtle, Terrapene carolina. Archives Italiennes de Biologie 112: 227-252.
French, A.R., 1982. Effects of temperature on the duration of arousal episodes during hibernation. Journal of Applied Physiology 52: 216-220.
Gaffney, F.G. and L.C. Fitzpatrick, 1973. Energetics and lipid cycles in the lizard Cnemidophorus tigris. Copeia 1973: 446-452.
Gatten, R.E., Jr., 1978. Aerobic metabolism in snapping turtles, Chelydra serpentina, after thermal acclimation. Comparative Biochemistry & Physiology A 61: 325-337.
Gelineo, S., 1967. Oxygen consumption in lizards on the way to winter sleep. Bulletin of the Academy of Serbe Sciences 39: 51-57.
Gregory, P.T., 1982. Reptilian Hibernation, Chapter 2. Pp 53-154 in Biology of the Reptilia, Volume 13; Physiology D, Physiological Ecology. C. Gans and F.H. Pough (eds.). Academic Press, London.
Hartse, K.M., S.F. Eisenhart, B.M. Bergmann, and A. Rechtschaffen, 1979. Ventral hippocampus spikes during sleep, wakefulness, and arousal in the cat. Sleep 1: 231-246.
Heller, H.C. and S.F. Glotzbach, 1977. Thermoregulation During Sleep and Hibernation. Pp 147-188 in International Review of Physiology: Environmental Physiology II, Volume 15. D. Robertshaw (ed.). University Park Press, Baltimore.
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when I rehabbed bats they would go into torpor in the winter and each day to feed them i'd have to warm them in my hands and rub them to 'wake them up ' and they'd do this cool vibration thing to get themselves ready to eat. 
