116 ANIMAL LIFE 



est breeder of all known animals. It begins breeding when 

 thirty years old and goes on breeding until .ninety years 

 old, bringing forth six young in the interval, and surviving 

 till a hundred years old. If this be so, after about eight 

 hundred years there would be 19,000,000 elephants alive, 

 descended from the first pair." A few years more of the 

 unchecked multiplication of the elephant and every foot of 

 land on the earth would be covered by them. 



Yet the number of elephants does not increase. In gen- 

 eral, the numbers of every species of animal in the state of 

 Nature remain about stationary. Under the influence of 

 man most of them slowly diminish. There are about as 

 many squirrels in the forest one year as another, about as 

 many butterflies in the field, about as many frogs in the 

 pond. Wolves, bears, deer, wild ducks, singing birds, fishes, 

 tend to grow fewer and fewer in inhabited regions, because 

 the losses from the hand of man are added to the losses in 

 the state of Nature. 



It has been shown that at the normal rate in increase of 

 English sparrows, if none were to die save of old age, it 

 would take but twenty years to give one sparrow to every 

 square inch in the State of Indiana. Such an increase is 

 actually impossible, for more than a hundred other species 

 of similar birds are disputing the same territory with the 

 power of increase at a similar rate. There can not be food 

 and space for all. With such conditions a struggle is set 

 up between sparrow and sparrow, between sparrow and 

 other birds, and between sparrow and the conditions of life. 

 Such a conflict is known as the struggle for existence. 



69. The struggle for existence. The struggle for exist- 

 ence is threefold : (a) among individuals of one species, 

 as sparrow and sparrow ; ( b) between individuals of differ- 

 ent species, as sparrow with bluebird or robin ; and (c) with 

 the conditions of life, as the effort of the sparrow to keep 

 warm in winter and to find water in summer. All three 

 forms of this struggle are constantly operative and with 



