SMALLER MAMMALS OF NORTH AMERICA 



485 



latest, like chipmunks and prairie-dogs, 

 sometimes appear temporarily during cer- 

 tain warm periods in winter. 



Recent observations have established 

 the fact that the adults of both sexes of 

 the Richardson ground-squirrel living in 

 the Northwestern States and adjacent 

 parts of Canada become excessively fat 

 by the first of July, and before the first 

 of August practically disappear for the 

 season, not appearing again until they 

 emerge the following March or April. 

 The retirement of these squirrels for a 

 part of the summer is a case of imperfect 

 estivation, as it is termed, followed by 

 complete hibernation. The young of the 

 year enter hibernation at a considerably 

 later date. 



defe;nsiv]5 and offensive animal 



AIvIvIANCES 



A great number of both large and small 

 mammals live solitary lives except for 

 brief periods during the mating season 

 or the association of the young with the 

 mother. Some species, however, like the 

 wolves and coyotes, may mate perma- 

 nently and show great mutual affection 

 and constancy. Many species have well- 

 developed social instincts, which appear 

 in some cases to combine two purposes, 

 self-defense and the desire for compan- 

 ionship. 



Herds of large herbivorous mammals, 

 such as musk-oxen and buffalo, fre- 

 quently present a solid array of bristling 

 horns to the attacking wolves, and thus 

 protect the weaker members of the herd 

 and give an example of the usefulness 

 to them of the social instinct. Wolves 

 and some other predatory animals hunt 

 in couples or in packs and succeed in 

 pulling down prey which singly they 

 could not successfully attack. 



Prairie-dogs living in colonies have the 

 advantage of community intercourse as 

 well as added safety through the chance 

 that some member of the colony will espy 

 an approaching enemy and by its warn- 

 ing cry allow a safe retreat. In other 

 cases, such as the flying-squirrels, which 

 gather in considerable numbers in hollow 

 trees or other shelter, and the bats, which 

 gather in caves, the congregation appears 

 to be purely from a desire for close com- 

 panionship. 



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FOOTPRINTS OF NATURE'S WILD FOLK 

 BY ERNEST THOMPSON SETON 



In the drawings accompanying Mr. Nelson's 

 article I usually give the track of a normal 

 adult animal in about one inch of snow, that 

 being ideal for tracking. Some of the smaller 

 kinds are shown in fine dust. The trail goes 

 up or across the page at the ordinary gait of 

 the animal. The scale is indicated, but when 

 possible the topmost set is given of life size. 

 While there are endless variants in each kind, 

 I aim to give the reader at least one typical 

 set of each. 



In all animals which bound, the hind feet 

 track ahead of the front ones. This is very 

 plainly seen in the rabbits. There are two ar- 

 rangements of the fore feet when bounding : 

 That of the rabbit (b), in which the fore feet 

 are usually one behind the other, and that of 

 the tree-squirrel (a), in which the fore feet are 

 side by side. The latter arrangement is associ- 

 ated with power to climb a tree. The former 

 means that the animal is purely terrestrial. 

 These, however, are true only as generaliza- 

 tions. There are exceptions in all species. The 

 ground-squirrels conform to the rabbit type. 

 The tracks are, of course, ideal, giving far 

 more detail than is usually to be seen. 



