140 ILLINOIS STATE ACADEMY OF SCIENCE 



THE SHIFTING OF THE MAMMALIAN FAUNAS, 



AS SHOWN BY THE PLEISTOCENE REMAINS 



OF ILLINOIS* 



L. A. Adams, University of Illinois 



A study of the fauna of any region, extending over a 

 short period of time, will show certain changes in the ani- 

 mal population that are due entirely to natural causes; 

 since conditions change, food animals become reduced in 

 numbers through drouths or extended winters, and the 

 correlated animals must move and re-adjust their num- 

 bers. Many of these shifts in the population appear to 

 be without cause and are due simply to the wandering 

 spirit, while others are correlated closely with actual 

 changes in conditions. A study of a region for a long 

 period of time will show marked changes and a great re- 

 duction or a complete dropping of the large groups. 

 Sometimes descendants are left in the original home; 

 sometimes survivors are to be found in regions far dis- 

 tant from the original home; sometimes entire groups 

 disappear and leave no traces behind them but their 

 bones in the rocks. 



When man enters a region, rapid changes are likely 

 to take place in a very short time. He first hunts and 

 traps until certain animals are reduced or exterminated. 

 The hunter is followed by the rancher who fences large 

 areas, or leaves it open and grazes it, and as a conse- 

 quence eliminates certain types of the fauna. The next 

 man to follow is the farmer or agriculturist who fences 

 and cultivates the land, cuts off the forests, drains 

 the lakes and swamps, and changes the water courses. 

 As cities grow up, the water courses are contaminated 

 with their waste until they cannot support life, and an- 

 other portion of the fauna disappears. A survey of Illi- 

 nois for the last hundred years will show just such a 

 shift, with the larger animals and many of the smaller 

 ones driven out or reduced by the activities of man. The 

 bison, deer, bear, beaver, and even the wolves have left 

 us, although the wolf will remain longer than almost any 



• Contribution from the Zoological Laboratory of the University of 

 Illinois. 



