. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 84 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY Vol. 124 Accordingly, the critical ambient tempo rat lire may represent a limiting condition, and only below this value could our (north- ern) hibernators lower their TB by failing to supply heat for thermoregulation. Model curves for two animals of different size are given in Figure 7. The 40 g animals (, a jumping mouse) could cool below 25°, but the 4 kg animal (, a large marmot) would need a temperature of less than 5° to cool. Of course, these relations are base
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 84 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY Vol. 124 Accordingly, the critical ambient tempo rat lire may represent a limiting condition, and only below this value could our (north- ern) hibernators lower their TB by failing to supply heat for thermoregulation. Model curves for two animals of different size are given in Figure 7. The 40 g animals (, a jumping mouse) could cool below 25°, but the 4 kg animal (, a large marmot) would need a temperature of less than 5° to cool. Of course, these relations are based on the standard curve of metab- olism and weight, in which Mann at a is a conspicuous exception with a metabolic rate about one-half the ''predicted" value (Benedict and Lee, 1938). Thus, the critical temperature for M/M. TA IN °C Fi^'. 7. Model curves for two animals showing the influence of .size and basal metabolic rate on the critical temperature, below which the body temperature can be reduced while metabolism remains at the basal level. the marmot would be 20°C, and not 5° which might be difficult to attain. One wonders if this correlation with hibernation function and considerable size could provide an explanation for the unusually low metabolic rate in this genus. The relation between conductance and weight is only valid up to a size of perhaps 50 kg since the fur length does not increase in larger animals. At this weight, however, the critical differen- tial would be 65° and the critical temperature — 30° Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Harvard University. Museum of Comparative Zoology. Cambridge, Mass. : The Museum
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