CHAPTER XXXI. 

 GROUPS OF MAMMALS. 



GROUPING SMALL MAMMALS. Since onr small mammals can 

 not migrate south in winter, as do the birds, each species must 

 provide itself with a winter home, or perish. The nesting and 

 burrowing 1 habits of these builders of " homes without hands " 

 afford a most interesting- field for investigation and study, and 

 one which is of great interest to everyone. Almost without 

 exception, every mammalian species found in the United States 

 below the size of the coyote, establishes for itself during a part, 

 if not the whole, of the year, a fixed habitation. Some of the 

 more enterprising species, notably the squirrels and rabbits, 

 enjoy the luxury of a summer residence as wt?ll as a winter 

 home. The groups of small mammals which the National Mu- 

 seum is now producing and placing upon exhibition have for 

 one of their principal features the illustration of the home- 

 making habits of the species represented. A mention of one 

 or two examples will serve to convey an idea of the type of 

 each class. 



A group of American opossums may be taken as a good ex- 

 ample. The case which encloses the entire group is 4 feet 

 long, 3 feet wide, and 3 feet high. The frame of the case 

 is as light as possible, and all four sides and the top are of 

 glass. On the side of a sloping bank stands the base of a small 

 gum-tree, with the roots on the lower side exposed by the 

 crumbling away of the bank. Of course the trunk rises to the 

 top of the case, where it is cut squarely off. At the bottom of 

 the sloping bank, between two of the roots, is an opening, 

 which is recognized at once as the doorway to the opossum's 

 home. The burrow winds upward between the roots of the 

 tree, and finally turns off to the left into the bank, Avhere, after 



