HOFFMEISTER & MOHR: ILLINOIS MAMMALS 13 



lication 7, University of Kansas Museum of Natural History; 

 and A Field Collector's Manual in Natural History, 1944, 

 Publication 3766, Smithsonian Institution. Washington, D. C. 

 The beginning collector should study these books carefully. 



SIGNS 



The study of mammal signs is one of the most interesting 

 pursuits available to a hiker. By practice in developing an eye 

 for details, the most observant hunters, trappers, and naturalists 

 are usually highly skilled in reading signs. The occasional hiker 

 can train himself to discern and interpret signs and thus add 

 considerable interest to his field trips. 



Most mammal signs fall into one of these six classes: homes, 

 trails and runways, tracks, scats or droppings, tooth marks, and 

 food stores and fragments. The interpretation of these signs is 

 a type of detective work, and it is largely a process of elim- 

 ination combined with a general knowledge of the mammals 

 occurring in the region. Several factors, such as the kind of sign, 

 size and form of the sign, ranges of mammals which could have 

 made such a sign, type of habitat, and season of the year, must 

 be considered in each case. For example, suppose the sign con- 

 sists of a set of small tracks in a snow-covered field adjacent to 

 a tree-lined ditch in southern Illinois. The size of the tracks 

 hint that the mammal is smaller than a cat but larger than a 

 rat, thus eliminating many species. The fact that ground squir- 

 rels, pocket gophers, and red squirrels do not occur in southern 

 Illinois removes them from consideration. The habitat suggests 

 that the animal is a forest-edge species, a prairie animal, or 

 even an aquatic species, but probably not an inhabitant of deep 

 woods, such as is the gray squirrel. The snow on the ground 

 precludes the possibility of a woodchuck, because this animal 

 would be in hibernation. The list of possible mammals still in- 

 cludes the fox squirrel, muskrat, mink, weasel, and cottontail. 

 A close scrutiny of the tracks reveals that the toe marks are long 

 and slender, thus ruling out the cottontail, weasel, and mink, but 

 leaving the fox squirrel and the muskrat. The tracks can be 

 compared with sketches of muskrat and fox squirrel tracks, figs. 

 21 and 34; these sketches indicate that the muskrat is likely to 

 leave some trace of a tail mark. If a tail mark is present, it is 

 likely that the tracks were made by a muskrat. 



