THE NORTH AMERICAN FAUNA 169 



THE FUTUEE OF THE NOETH AMEEICAN FAUNA 



By the late WALTER L. HAHN, Ph.D. 



THAT the animal life of North America is changing is a statement 

 requiring no proof. Every one knows that deer, elk, moose, 

 wolves, hison and many other animals are no longer found in places 

 where they were once numerous. Nearly every one also knows that 

 some pests, such as rats and mice and several noxious insects, have 

 been brought to this country from Europe, while the potato beetle and 

 some other species, natives of North America, have multiplied and 

 extended their range. 



It is impossible, within the limits of this paper, to specify all 

 the changes that have taken place and are now in progress. Hence it 

 will be my aim to point out certain general tendencies, and certain 

 general influences at work upon our fauna, the word fauna being a 

 somewhat technical term used to designate the sum total of the animal 

 life, great and small, in any circumscribed region. 



If asked why the great game animals have disappeared from certain 

 regions, most people would doubtless say, " Indiscriminate slaughter 

 has exterminated them." This answer is undoubtedly correct as far as 

 it goes. For a full explanation of all of the changes that have taken 

 place in our fauna we must seek deeper reasons. Why has not " indis- 

 criminate slaughter " exterminated the mice and rats and other noxious 

 creatures against which we have waged ceaseless war for many genera- 

 tions ? In other words, what are the biological and physical conditions 

 that determine whether an animal species shall survive or perish in 

 modern America? 



A living organism, even the simplest, is a thing of vastly greater 

 complexity than any mere chemical compound or any physical law. 

 We know how to kill individual organisms, but frequently we do not 

 know what will exterminate a species. If a lion and a lamb lie down 

 together, we know which will be on the inside. But if a given number 

 of lions and a given number of lambs inhabit a great area we can not 

 predict the exact results; and this illustrates the futility of trying to 

 make a definite analysis of the future of any particular species. 



I shall now consider the future of North American animals from 

 the general standpoints of size, habitat, relation to man, fecundity, 

 mental traits, and finally give a few interesting facts not comprehended 

 in the above classification. 



VOL. LXXXIII. — 12. 



