CANADA PORCUPINE 5 



important to note that, though the captured animals were in 

 natural temperature and had dark, cozy dens xtith an outside 

 run where snow was abundant, experimentation continued until 

 December 23rd with no appreciable diminution in their activity. 

 In addition it was noted that throughout the remaining part 

 of the winter their activity was in no way lessened even by a 

 temperature of — 15° F. Furthermore, a visit to the dens in 

 the wild, when the temperature was far below zero and the 

 snow 36 inches deep, showed the trails broken and the feeding 

 grounds being used by them regularly. 



Humidity has been found far more potent than temperature 

 in determining their activity. It became a regular custom 

 during this study to predict rain whenever the animals in cap- 

 tivity were observed to be more active than, usual, although 

 they can hardly serve as a standard barometer as certain writers 

 have suggested. It has also just as frequently happened that 

 they were quiet on a dull, rainy day. These observations are 

 all the more interesting in that these phenomena have been 

 fairly constant and simultaneous with from five to seven animals 

 and in that they have been more marked in newly captured 

 animals, where the natural instincts of food-getting have been 

 least disturbed. In addition, it was noted that while captur- 

 ing animals in the month of vSeptember, there was a close cor- 

 relation between barometric disturbances and the number of 

 snares which were thrown, probabl3^ though not certainly, by 

 the porcupines. In explanation, it should be said that the 

 animal's exposure in the trees while feeding, as well as in the 

 grass and weeds while going to and from the feeding grounds, 

 taken with the fact that his coat is not impervious to water, 

 would, no doubt, select and fix a tendency to feed as the baro- 

 metric pressure was lowering. Similar observations- have been 

 made on hogs building a bed before a storm and on deer coming 

 down from the hills when the warm south winds begin to blow. 

 It would be interesting to know whether such an instinctive or 

 habitual motor response is brought about by humidity or whether 

 the stimulus is an olfactory one. Are the odors of the forest 

 different in moist air? Does the presence of water vapor in 

 the air lower the limen of olfaction? Such questions are hardly 

 answerable for people, but might well be considered with animals 

 where the sense of smell mav be more acute. 



