MAN AND NATURE 9 
interfere with any animals or the habitats of any animals without inter- 
fering with many others. The second is that all animals are of some 
economic importance. The third, that few animals can be said to be 
either wholly beneficial or wholly noxious, excepting those reared or 
preserved for their direct utility, and those directly and perniciously 
attacking the necessities of man’s existence. 
Considering the first, we note that civilized man’s operations interfere 
with animals and animal habitats. His first work is to destroy all large, 
dangerous animals. He clears and cultivates the land, bringing death 
and destruction to many more, and gradually substitutes domestic ani- 
mals for wild game (5a). Vegetarians often argue for the exclusive use 
of vegetable food on the ground that animals should not be killed, but 
to secure more plants for this purpose they of necessity would clear more 
land to grow more corn and thus destroy myriads of animals by methods 
more cruel than those of the butcher and huntsman. Our relations to 
animals are not simple, but very complex and our conduct often inconsist- 
ent. We cease wearing aigrettes because the collecting of them often 
leaves young birds to die, and kill every mouse and mole that happens 
to come our way, though their young must die as do those of the birds. 
Some of us wear leather shoes while arguing for a vegetarian diet because 
animals should not be cruelly slaughtered. 
Turning to the second and third ideas stated above, we note that 
few animals which feed upon a variety of foods, both plant and animal, 
can be said to be of any great usefulness, except when the plants eaten 
are useless to man. In other words, the good done the farmer by an 
animal which eats many insects, including noxious ones, may be offset 
by a destruction of grain. Birds eat a variety of food. Those feeding 
upon useful plants are not rated as of great economic importance. The 
bobolink, for example, eats grain and weed seeds in the spring when 
insects are scarce; soft-bodied insects in June and July when seeds are 
not available. In August the insects mature and are hard shelled. The 
birds now reject them for the grain seeds. This bird, furthermore, eats 
that which is available and most easily secured during the different 
seasons. This is also true of many, probably the vast majority of 
animals. The food of fishes is to a considerable extent determined by 
the kind of food available where they are living (6). Ruthven (7) has 
found this true of garter-snakes; the same is true of men. 
Many animals, birds (8), mammals, reptiles (9), toads (10), and 
insects destroy quantities of noxious insécts, but along with them many 
insects that are enemies and parasites of the noxious ones are also 
