Ill 



THE ECONOMIC RELATIONS OF MAMMALS IN GENERAL 



The investigation of wild birds has taught us that most of the 

 species are more useful than harmful and many of them almost alto- 

 gether useful. A large proportion of the species of mammals also are 

 either useful or comparatively harmless, but the proportion of in- 

 dividual mammals that are very harmful is probably much greater than 

 in case of birds. This is due to the fact that the most abundant mam- 

 mals belong to the Rodentia, which order includes many very destruc- 

 tive groups, such as prairie-dogs, gophers, rats and mice, that increase 

 very rapidly under favorable circumstances. Much damage is also done 

 by beasts of prey of the cat and dog families, such as the tiger, lion, 

 leopard, puma, lynx, wolf, coyote and fox, though some or all of them 

 also do more or less good to offset their iniquities. Some of the fur- 

 bearing mammals (weasels, skunks, etc.) are destructive to poultry and 

 wild birds, though they, too, have some useful habits. 



Though economic mammalogy is a very large and complex subject, 

 with many ramifications, it centers about four main questions, namely : 

 What species are useful or harmless and entitled to reasonable pro- 

 tection? How may they best be encouraged and protected? What 

 species are more harmful than useful and should be kept in check? 

 How may they best be controlled or destroyed, or the damage they do 

 be minimized? 



That all sounds perfectly simple and easy, but one soon discovers 

 many complications. A species that is not very injurious or is even 

 definitely useful under ordinary circumstances may, under other cir- 

 cumstances, temporarily become exceedingly injurious. For example, 

 meadow mice in most localities are not usually abundant enough to do 

 a great amount of damage, but when, during favorable seasons, their 

 numbers are enormously augmented by a low mortality rate and high 

 fecundity, they become a menace. In an unsettled region, infested by 

 an overabundance of rabbits, prairie-dogs and ground squirrels, a few 

 coyotes to keep those rodents in check may be quite useful, but with 

 the advent of stock and poultry raising a marked increase in the coyote 

 population would make them quite harmful in the destruction of poul- 



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