The effect of large body size on the temperature regulation of the komodo dragon, Varanus komodoensis

McNab, Brian K.; Auffenberg, Walter

doi:10.1016/0300-9629(76)90058-x

Cited by 89 publications

(47 citation statements)

References 19 publications

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“…This strategy might have functioned optimally in the relatively mild, equable climatic regimes of most of the Mesozoic Era, where chronic maintenance of ectothermic homeothermy would have been possible (as in the Varanus komodoensis [McNab and Auffenberg 1976;Spotila et al 1991]). …”

Section: Discussionmentioning

confidence: 99%

“…In addition, some particularly large ectotherms (e.g., Komodo dragons [Varanus]) living in warm, equable climates remain virtually homeothermic for long periods in their natural environments. In such cases, these animals achieve "inertial homeothermy" by virtue of their minimal surface-area-to-volume ratios and correspondingly low heat loss rates (Frair et al 1972;McNab and Auffenberg 1976;Standora et al 1984;Paladino et al 1990).…”

Section: Metabolism and Thermoregulation In Amniotes Living And Extinctmentioning

confidence: 99%

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Respiratory and Reproductive Paleophysiology of Dinosaurs and Early Birds

Ruben

Jones²,

Geist³

2003

Physiological and Biochemical Zoology

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In terms of their diversity and longevity, dinosaurs and birds were/are surely among the most successful of terrestrial vertebrates. Unfortunately, interpreting many aspects of the biology of dinosaurs and the earliest of the birds presents formidable challenges because they are known only from fossils. Nevertheless, a variety of attributes of these taxa can be inferred by identification of shared anatomical structures whose presence is causally linked to specialized functions in living reptiles, birds, and mammals. Studies such as these demonstrate that although dinosaurs and early birds were likely to have been homeothermic, the absence of nasal respiratory turbinates in these animals indicates that they were likely to have maintained reptile-like (ectothermic) metabolic rates during periods of rest or routine activity. Nevertheless, given the metabolic capacities of some extant reptiles during periods of elevated activity, early birds were probably capable of powered flight. Similarly, had, for example, theropod dinosaurs possessed aerobic metabolic capacities and habits equivalent to those of some large, modern tropical latitude lizards (e.g., Varanus), they may well have maintained significant home ranges and actively pursued and killed large prey. Additionally, this scenario of active, although ectothermic, theropod dinosaurs seems reinforced by the likely utilization of crocodilian-like, diaphragm breathing in this group. Finally, persistent in vivo burial of their nests and ap-*

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Section: Discussionmentioning

confidence: 99%

Section: Metabolism and Thermoregulation In Amniotes Living And Extinctmentioning

confidence: 99%

Respiratory and Reproductive Paleophysiology of Dinosaurs and Early Birds

Ruben

Jones²,

Geist³

2003

Physiological and Biochemical Zoology

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“…Aggressively predatory lizards of the genus Varanus, including the largest living lizard, the Komodo dragon (V. komodoensis), which feeds on deer, pigs, and occasionally water buffalo and people (19), have FEEs that average 3.6 times those of most lizards (11) (Fig. 3), reflecting their high level of activity and high body temperatures (20). The relationship between FEE and body mass in 6 species of varanids, weighing 2.2 to 45.2 kg, is 1.07g 0.735 (r 2 ϭ 0.964), which is 22% of mammalian FEEs of equal size (Fig.…”

Section: Resultsmentioning

confidence: 99%

Resources and energetics determined dinosaur maximal size

McNab

2009

Proc. Natl. Acad. Sci. U.S.A.

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Some dinosaurs reached masses that were Ϸ8 times those of the largest, ecologically equivalent terrestrial mammals. The factors most responsible for setting the maximal body size of vertebrates are resource quality and quantity, as modified by the mobility of the consumer, and the vertebrate's rate of energy expenditure. If the food intake of the largest herbivorous mammals defines the maximal rate at which plant resources can be consumed in terrestrial environments and if that limit applied to dinosaurs, then the large size of sauropods occurred because they expended energy in the field at rates extrapolated from those of varanid lizards, which are Ϸ22% of the rates in mammals and 3.6 times the rates of other lizards of equal size. Of 2 species having the same energy income, the species that uses the most energy for mass-independent maintenance of necessity has a smaller size. The larger mass found in some marine mammals reflects a greater resource abundance in marine environments. The presumptively low energy expenditures of dinosaurs potentially permitted Mesozoic communities to support dinosaur biomasses that were up to 5 times those found in mammalian herbivores in Africa today. The maximal size of predatory theropods was Ϸ8 tons, which if it reflected the maximal capacity to consume vertebrates in terrestrial environments, corresponds in predatory mammals to a maximal mass less than a ton, which is what is observed. Some coelurosaurs may have evolved endothermy in association with the evolution of feathered insulation and a small mass.ectothermy ͉ endothermy ͉ energy expenditure ͉ varanid lizards W hether dinosaurs were endotherms or ectotherms has been controversial, as has been whether their thermal biology had any relevance to their attainment of extraordinarily large masses. Some authors (1-4) maintained that dinosaurs must have been endotherms because of their size, upright posture, bone structure, growth rates, presumed level of activity, and the high-latitude distributions of some species. Others (5-9) suggested that dinosaurs had a thermally constant body temperature as a result of large masses and small surface-to-volume ratios, but they probably had much lower levels of energy expenditure than would be expected of mammals (or birds) of the same mass, which was indicated by intermediate growth rates, narrow nasal passages, and unmodified, bellows-like septate lungs, which implies low ventilation rates. What most of these analyses have neglected is that the consumed resources ultimately control the energy expenditure and body size of organisms. Here, I propose that the maximal size of vertebrates is determined by resource abundance and how it is used by species.A Model. The maximal size of vertebrates is limited principally by the abundance and quality of the resources used to sustain their activities. The maximal daily field expenditure (K, kJ/d) of an individual varies with a variety of factors, including its mass, mobility, and the foods consumed. For example, the maximal expenditures (K h ) and...

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“…Large reptiles, including giant dinosaurs, might have had relatively constant body temperatures (Colbert et al, 1946;Bakker, 1972;McNab and Auffenberg, 1976;Barrick and Showers, 1994). Theoretical simulation has raised the interesting idea that large reptiles might maintain a high body temperature as a result of large size alone (Spotila et al, 1973;Stevenson, 1985).…”

Section: Introductionmentioning

confidence: 99%

Body temperature stability achieved by the large body mass of sea turtles

Sato

2014

Journal of Experimental Biology

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To investigate the thermal characteristics of large reptiles living in water, temperature data were continuously recorded from 16 free-ranging loggerhead turtles, Caretta caretta, during internesting periods using data loggers. Core body temperatures were 0.7-1.7°C higher than ambient water temperatures and were kept relatively constant. Unsteady numerical simulations using a spherical thermodynamic model provided mechanistic explanations for these phenomena, and the body temperature responses to fluctuating water temperature can be simply explained by a large body mass with a constant thermal diffusivity and a heat production rate rather than physiological thermoregulation. By contrast, body temperatures increased 2.6-5.1°C in 107-152 min during their emergences to nest on land. The estimated heat production rates on land were 7.4-10.5 times the calculated values in the sea. The theoretical prediction that temperature difference between body and water temperatures would increase according to the body size was confirmed by empirical data recorded from several species of sea turtles. Comparing previously reported data, the internesting intervals of leatherback, green and loggerhead turtles were shorter when the body temperatures were higher. Sea turtles seem to benefit from a passive thermoregulatory strategy, which depends primarily on the physical attributes of their large body masses.KEY WORDS: Data logger, Heat production rate, Thermal conductivity, Thermal diffusivity, Thermal inertia, Unsteady model INTRODUCTIONLarge reptiles, including giant dinosaurs, might have had relatively constant body temperatures (Colbert et al., 1946;Bakker, 1972;McNab and Auffenberg, 1976;Barrick and Showers, 1994). Theoretical simulation has raised the interesting idea that large reptiles might maintain a high body temperature as a result of large size alone (Spotila et al., 1973;Stevenson, 1985). Seebacher et al. (Seebacher et al., 1999) have previously used field data to demonstrate that high and stable body temperatures of land-living crocodiles are driven primarily by physical relationships between body temperature and environmental temperature. Water, in comparison with air, places much tighter constraints on thermoregulation in aquatic animals, owing to its high heat capacity and high thermal conductivity, which leads to a rapid transfer of heat from a warm animal to cold water. Thus, water strongly limits the warming effect of metabolism in aquatic living animals.Sea turtles spend almost all their time under water, and their range of both vertical and horizontal movements are large. To substantiate their thermal characteristics under natural conditions, long and RESEARCH ARTICLEAtmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan. continuous measurements in the sea were needed. Some aspects of body temperature of free-ranging turtles during the internesting period have been revealed previously using animal-borne recorders (Sakamoto et al., 1990;Sato et...

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The effect of large body size on the temperature regulation of the komodo dragon, Varanus komodoensis

Cited by 89 publications

References 19 publications

Respiratory and Reproductive Paleophysiology of Dinosaurs and Early Birds

Respiratory and Reproductive Paleophysiology of Dinosaurs and Early Birds

Resources and energetics determined dinosaur maximal size

Body temperature stability achieved by the large body mass of sea turtles

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