. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. I960 MAMMALIAN I UBKRNATK »N 161 studies I discerned a seasonal variation in rcdal temperature in active squirrels. Figure f> shows this variation in wild squirrels plotted against date. There is no apparent relation to ambient temperature, sex, or degree of* fatness. Figure ti shows averages of rectal temperatures of about 100 captive squirrels kept at 10°C, approximately the average temperature of the wild squir- rel's habitat. There is a progressive fall in temperature under u o a. 36 I-. ib~ 20 I 30 20 JUNE 15
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. I960 MAMMALIAN I UBKRNATK »N 161 studies I discerned a seasonal variation in rcdal temperature in active squirrels. Figure f> shows this variation in wild squirrels plotted against date. There is no apparent relation to ambient temperature, sex, or degree of* fatness. Figure ti shows averages of rectal temperatures of about 100 captive squirrels kept at 10°C, approximately the average temperature of the wild squir- rel's habitat. There is a progressive fall in temperature under u o a. 36 I-. ib~ 20 I 30 20 JUNE 15 JULY 40 50T 31 JULY IIAUG 6b |70 26 AUG 36 100 II SEPT 23SEPT no; 120 |i3o 8 OCT 23 OCT DAYS a DATES Fig. 6. Average rectal temperatures of captive Arctic ground squirrels plotted against date. these captive conditions which is not discernible in the wild squirrels until just prior to the onset of hibernation. This points up the fact that data on captive animals is not necessarily valid for extension to the wild or natural state. Therefore, it appears that wild ground squirrels exhibit four different phases of tem- perature control during the year, as follows: (1 ) the low tempera- tures found during hibernation; ('2) the variable temperatures found for a short period after emergence ; (3) high and relatively constant temperatures during most of the active season; (4) falling temperatures just prior to entrance into hibernation. During hibernation, temperatures close to ambient are re- corded. Normally, I have kept my animal quarters at 4° -2°C,. 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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