HOFFMEISTER & MOHR: ILLINOIS MAMMALS 19 



2. A more irregular mound, fig. 7, lacking the visible indi- 

 cation of subsurface runs and the symmetry of the mole mound, 

 is typical of pocket gophers. This is usually a rough crescent 

 with a small pustule midway between the tips of the crescent. 



3. A hole with a mound of earth to one side and trash scat- 

 tered about, fig. 8, is typical of Norway rats. 



4. A hole in a grassy area with a flat bare area to one side is 

 typical of thirteen-lined ground squirrels. 



There are, of course, many variations from the typical bur- 

 rows described above. 



Homes Above Ground. — Many species of mammals make 

 grassy or leafy nests on the ground or in shrubs or trees. Mam- 

 mal nests are almost invariably roofed over, not open as many 

 birds' nests are, and they do not have the nest materials plastered 

 together with mud or secretions. However, certain mammals 

 reconstruct birds' nests for their own homes. For this reason 

 the only sure way to ascertain the inhabitant of a covered nest 

 is to see the inhabitant as it enters or leaves the nest or to ex- 

 amine the nest for the presence of eggs, young, or an adult. 



Mammal homes above ground may be divided conveniently 

 into three categories: arboreal, hidden terrestrial, and aquatic. 



Arboreal nests include those made in trees, in bushes, or in 

 tufts of herbaceous plants. Several distinctive types may be 

 found, as follows: 



1. Nests made in hollows of trees. These may be utilized as 

 home sites by raccoons, opossums, fox squirrels, or gray squir- 

 rels, flying squirrels, bats, white-footed mice, and even gray foxes 

 or bobcats. 



2. Large exposed nests high in trees. These may be the homes 

 of tree squirrels, fig. 9; if deserted by the original owners, they 

 may be occupied by raccoons, bats, or sometimes flying squirrels. 

 At a distance these nests look like crows' nests but they may be 

 distinguished by being completely roofed over and usually being 

 composed of leaves rather than of sticks and leaves. 



3. Smaller nests in bushes or herbaceous plants near the 

 ground. These nests are made chiefly of dry grass or of plant 

 "down." Many small mammals have nests of this type. These 

 nests may be entirely the work of the mammals occupying them 

 or they may be reconstructed birds' nests. Such homes are 

 characteristic of golden mice, fig. 91, cotton mice, white-footed 

 mice, and rice rats. 



