HOFFMEISTER & MOHR: ILLINOIS MAMMALS 25 



food fragments may be available to aid in eliminating some 

 species from consideration. 



Slides are worn troughs on muddy stream banks where otters, 

 minks, or muskrats have slid into the water. 



Tracks. — Tracks are among the most reliable signs for iden- 

 tifying mammals, but their characteristics must be memorized or 

 the tracks compared directly to sketches of known kinds of 

 tracks. Tracks of many mammals native to Illinois are illus- 

 trated in the accompanying plates. With a little practice in 

 identifying tracks, a person can learn to recognize many of 

 these at a glance. 



Kinds of Tracks. — The kind of track a mammal makes de- 

 pends upon whether it is walking, trotting, or running. Tracks 

 made by an animal when running have individual footprints far- 

 ther apart than those made by the same animal when walking, 

 and often the footprints are arranged in a different pattern. 



In mud, moist sand, or snow, a mammal may make excellent 

 imprints of its feet and sometimes belly or tail. When made in 

 thick mud, the prints of the toes are usually spread more widely 

 than when made in a layer of thin mud. If distinctly made 

 tracks are found in Illinois, they may be identified through use 

 of the following key. 



Key to Tracks of Some Common Illinois Mammals 



1. Footprint consisting of one or a pair of solid impressions, 



figs. 15, 16 2 



Footprint consisting of three or more toe marks, figs. 17-30 6 



2. Each footprint less than 11? inches wide 3 



Each footprint more than 11/ inches wide 4 



3. Each set of 4 footprints with a pair tandem and a pair side 



by side, or almost side by side, fig. 16 rabbits 



Each set of 4 footprints arranged otherwise 



imperfect tracks of small mammals 



4. Each footprint a single subcircular mark horse 



Each footprint consisting of a pair of marks, fig. 15 5 



5. Each footprint 3 inches or more across cow 



Each footprint less than 3 inches across, fig. 15 



deer, goat, sheep, pig, calf 



6. Imprint of first and of fifth toe of front foot at almost 180- 



degree angle, fig. 17; axis of imprint of big toe of hind 

 foot well separated from and at an angle of at least 90 



degrees to axis of imprint of next toe oposMim 



Imprint of inner and of outer toe of front foot at less than 

 120-degree angle, figs. 18-36; imprint of inner and of 

 outer toe of hind foot at less than 90-degree angle 7 



