ADAPTATIONS TO TROPICS AND ALTITUDES 



state where the T approached the T . Also in bats here, as in 

 Miniopterus, there can be an intermeoiate zone (sleeping *<) — not 

 poikilothermic in the ordinary sense, but just a little above 30 C 

 where the animal can become active rather quickly, but still effect 

 an appreciable metabolic savings. Now, the T groups in the cold 

 exposed animals can be associated with these groups , although they 

 may not be exact projections. The upper curve (Fig. 14) maintains 

 the "resting" level and at 6 G ambient, as a more vigorous meta- 

 bolic response is required, even approaches the "active" level. 



The intermediate curve with T values near 30 maintained even 



o B . . 



at 6 G ambient, gives further credence to the concept of a mam- 



tained "sleeping" level. Finally a few much lower values (lower 



curve) would represent torpor although not as low as the ambient 



level. 



Figure 14 also compares Molossus, a tropical insectivorous 

 bat, which uniformly became torpid when exposed to cold, although 

 not quite to the degree expected of a similar temperate bat. Figure 

 15 shows the daily T cycle in this species (lower curve) which also 

 closely resembles tne behavior of our northern bats with elevated 

 activity at dusk and dawn and torpor during the day. Eisentraut (1950) 

 has discussed tropical insectivorous bats which he found to have a 

 broader "range of activity temperature" than their temperate rela- 

 tives and thus not ordinarily to enter into a state of torpor during 

 the day. This was certainly the case in the situations where Molossus 



was collected (T = 30°+ C) but in the laboratory at a T . of 26 C 



o A , ^ 



to 28 C it certainly entered torpor. 



In Figure 15, also, the curves for the 4 frugivorous bats are 

 compared. This set of curves presents an interesting sequence of 

 parameters in order of decreasing animal weight. Thus, in this 

 series, both the resting diurnal and the active nocturnal levels are 

 increasing, the rate of change between the two activity states is 

 decreasing, and the diurnal fall is postponed, although the nocturnal 

 rise is fairlysynchronousfor the several species. The insectivorous 

 Molossus fits into these sequences in all regards except weight, 

 since it is the smallest of the lot. It is not now possible to interpret 

 these systematic regularities, buttheyno doubt fit into some general 

 pattern of thermoregulatory properties. 



403 



