554 APPENDIX E 



Mr. Thayer insists, as vital to his theory, that partridges and other pro- 

 tectively colored animals owe their safety, not at all to being incon- 

 spicuously colored, that is, to being colored like their surroundings, but 

 to their counter-shading, to their being colored dark above and light 

 below. But as a matter of fact most small mammals and birds which 

 normally owe their safety to the fact that their coloration matches their 

 surroundings, crouch flat whenever they seek to escape observation; 

 and when thus crouched flat, the counter-shading on which Mr. Thayer 

 lays such stress almost, or completely, disappears. The counter-shading 

 ceases to be of any use in concealing or protecting the animal at the precise 

 moment when it trusts to its coloration for concealment. Small rodents 

 and small dull-colored ground birds are normally in fear of foes which 

 must see them from above at the critical moment if they see them at all; 

 and from above no such shading is visible. This is true of almost all the 

 small birds in question, and of the little mice and rats and shrews, and 

 it completely upsets Mr. Thayer's theory as regards an immense pro- 

 portion of the animals to which he applies it; most species of mice, for 

 example, which he insists owe their safety to counter-shading, live under 

 conditions which make this counter-shading of practically no consequence 

 whatever in saving them from their foes. The nearly uniform colored 

 mice and shrews are exactly as difficult to see as the others. 



Again, take what Mr. Thayer says of hares and prongbucks. Mr. 

 Thayer insists that the white tails and rumps of deer, antelope, hares, 

 etc., help them by "obliteration" of them as they flee. He actually 

 continues that "when these beasts flee at night before terrestrial enemies, 

 their brightly displayed sky-lit white sterns blot out their foreshortened 

 bodies against the sky." He illustrates what he means by pictures, and 

 states that "in the night the illusion must often be complete, and most 

 beneficent to the hunted beast," and that what he calls "these rear-end 

 sky-pictures are worn by most fleet ruminants of the open land, and by 

 many rodents with more or less corresponding habits, notably hares" and 

 smaller things whose enemies are beasts of low stature, like weasels, minks, 

 snakes, and foxes; "in short, that they are worn by animals that are 

 habitually or most commonly looked up at by their enemies." Mr. 

 Thayer gives several pictures of the prongbuck, and of the northern 

 rabbit, to illustrate his theory, and actually treats the extraordinarily 

 conspicuous white rump patch of the prongbuck as an "obliterative" 

 marking. In reality, so far from hiding the animal, the white rump is at 

 night often the only cause of the animal's being seen at all. Under 

 one picture of the prongbuck, Mr. Thayer says that it is commonly 

 seen with the white rump against the sky-line by all its terrestrial 

 enemies, such as wolves and cougars. Of course, as a matter of fact, 

 when seen against the sky-line, the rest of the prongbuck's silhouette is 

 so distinct that the white rump mark 1 as not the slightest obliterative 

 value of any kind. I can testify personally as to this, for I have seen 

 prongbuck against the sky-line hundreds of times by daylight, and at 

 least a score of times by night. The only occasion it could ever have 



