HOFFMEISTER & MOHR: ILLINOIS MAMMALS 9 



The number of wild mammals that can be observed in an 

 area may be increased by improving the habitat for them. 

 Where there is a scarcity of suitable places for nesting and 

 hiding, and little available food, the mammalian population is 

 very low. In agricultural areas, cultivation may be so intensive 

 that few places are left that are suitable for mammals. Some- 

 times a few changes in these situations will increase the number 

 of mammals which can live there. In a wood lot having few 

 hollow trees, the addition of some nest boxes fastened in the 

 trees may provide homes for raccoons, squirrels, and opossums. 

 A fence of multiflora roses should provide sanctuary for cotton- 

 tails and mice. A ditchbank on which grass and other vegetation 

 are allowed to flourish will produce many more muskrats than 

 one that is grazed, mowed, or denuded. The removal of brush 

 and rotting logs from a wood lot destroys the habitat of mice 

 and squirrels and, indirectly, of other animals that feed on these 

 small mammals. 



Making a Collection of Preserved Specimens. — If one 

 wishes to make a survey of the mammals occurring in an area, 

 he should collect and prepare specimens of at least the small 

 animals so that they may be identified accurately. Securing 

 specimens of the various species is usually accomplished by hunt- 

 ing or trapping. Snap-traps are best for trapping small animals. 

 Some specimens can be found in steep-sided excavations such as 

 dry cisterns, window w r ells, post holes, and deep ditches into 

 which they have fallen. Often, revisits to such places are profit- 

 able because animals of different species may fall in at different 

 times. Mammals as large as or larger than rats may be shot or 

 trapped. Because most of them are protected by law, special 

 permission must be obtained unless they are collected only dur- 

 ing the hunting season, when they may be taken under an ordi- 

 nary hunting or trapping license. Highways may yield some 

 specimens that have been killed, but not badly mutilated, by 

 cars. 



A specimen that is small may be prepared for a study collec- 

 tion in one of the following ways. If only the skeleton is de- 

 sired, the animal is skinned, eviscerated, and dried; later it may 

 be cleaned by a culture of dermestid beetles. If for special rea- 

 sons preservation of the whole animal is desired, it can be kept 

 in 10 to 15 per cent formalin in a glass jar. Newly born young 

 are often preserved in this manner. The recommended method 



