494 APPENDIX E 



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 prong-bucks. 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 has 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 

 such obliterative value would be at the precise moment when it happened 

 to be standing stern-on in such a position that the rump was above the 

 sky-line and all the rest of the body below it. Ten steps further back, 

 or ten steps further forward, would in each case make it visible instantly 

 to the dullest-sighted wolf or cougar that ever killed game, so that Mr. 

 Thayer's theory is of value only on the supposition that both the prong- 

 buck and its enemy happen to be so placed that the enemy never glances 

 in its direction save at just the one particular moment when, by a combi- 

 nation of circumstances which might not occur once in a million times, 

 the prongbuck happens to be helped by the obliterative quality of the 



