90 ECOLOGY Part II 



generally the prey of larger ones, that there are great numbers of small animals 

 and relatively few large ones. This food situation is very complex. It clearly 

 involves sizes of food; it also includes feeding equipment such as cilia, teeth, 

 and claws, all sorts of locomotion, and kinds and extent of territory covered 

 in hunting food, as well as shifts in population due to cataclysms from the 

 action of weather and humanity. The food relations of animals, actually the 

 connections between the soil and the beefsteak, are exceedingly important to 

 human economy. 



Protecrive Resemblance and Mimicry. Protective resemblances are charac- 

 teristics that seem to make life safer for animals in their own environments. 

 Such protection is a debatable subject which has much to be shown for it and 

 considerable against it. It is a pattern of colors that makes an animal unrecog- 

 nizable against its home background. A brown streaked sparrow is lost among 

 the twigs of a brush pile; katydids are as green as the leaves beneath them; 

 ground squirrels (gophers) and prairie chickens are streaked Hke prairie grass; 

 fishes that swim in and out between bright-colored corals are also brightly 

 colored. Polar bears are white. Snowshoe rabbits and weasels (white phase is 

 ermine) are brown during the short northern summer and white in winter. 

 There are vast numbers of animals whose coloration does conceal; there are 

 also many in which it does not. There are animals whose coloration seems to 

 have no significance in their survival. Throughout the Arctic there are two 

 color phases of arctic foxes, one of them is brown in summer and white in 

 winter; the other is grey or black in summer and blue or black in winter. Both 

 the blue and white phases interbreed and are common and successful in the 

 same areas of Greenland and Alaska. 



Camouflage is the painting or screening of boats, buildings, other objects, 

 or persons so that they are lost to view in the background. It was first widely 

 used in World War I. Its principles were based upon those of protective 

 coloration suggested by a British zoologist, E. B. Poulton, and later developed 

 by an American artist, G. H. Thayer, and published in his finely illustrated 

 book. Concealing Coloration in the Animal Kingdom. The first of the princi- 

 ples is counter-shading, a generalization of the fact that in the great majority 

 of animals the back is dark and the underparts are pale. By painted models 

 Thayer showed that any object so colored is less conspicuous on being strongly 

 lighted from above and with dark reflection from below. Another principle is 

 related to the break-up of a familiar form such as that of a dark-colored bird 

 whose head is separated from its body by a white ring around the neck. 



Colors of animals are often strikingly different in the two sexes, the males 

 usually the more brightly colored, especially in birds, fishes, and insects. 

 Sexual coloration is often associated with endocrine secretions and is men- 

 tioned further in connection with them (Chap. 15). 



