506 APPENDIX E 



Probably it is an example of what is known as directive coloration, 

 of coloration used for purposes of advertisement or communication 

 with the animal's followers. But however this may be, it is certain 

 that there is not the smallest justification for Mr. Thayer's theory 

 so far as the prongbuck is concerned. 



It is practically the same as regards the rabbit or the hare. 

 Anyone who has ever been in the woods must know, or certainly 

 ought to know, that when hares are sitting still and trying to 

 escape observation, they crouch flat, so that the white of the tail 

 and rump is almost concealed, as well as the white of the under 

 parts, while the effect of the counter-shading almost or entirely 

 vanishes. No terrestrial foe of the hare would ever see the white 

 rump against the sky-line unless the animal was in rapid motion 

 (and parenthetically I may observe that even then it would only 

 see the rump against the sky-line in an infinitesimally small number 

 of cases). Of course, as soon as the animal is in motion it is 

 conspicuous to even the most dull-sighted beast of prey ; and 

 Mr. Thayer's idea that the white rear patch may mislead a foe as 

 it jumjjs upon it is mere supposition, unsustained by any proof, 

 antl contrary to all the facts that I have observed. Civilized man, 

 who is much more dull-sighted than most wild things, can always 

 see a rabbit when it runs because its white is then so very con- 

 s})icuous. Here, again, I do not think there is the slightest value 

 in Mr. Thayer's theory. The white rump is certainly not a pro- 

 tective or obliterative marking; it is probably a directive or 

 advertisement marking. 



The Virginia deer, utterly unlike the prongbuck, does often seek 

 to evade observation by lying close, or skulking. When it lies 

 close, it lies flat on the ground like a hare, and its white tail is 

 almost invisible, while of course even the most low-creeping foe 

 would not under such circumstances get it against the sky-line. 

 When it skulks, it moves off with head and neck outstretched and 

 tail flattened down, with the white as much obscured as possible. 

 The white is never shown in conspicuous fashion until the animal 

 is frightened and no lonoer seeks concealment. It then bounds off 

 openly, crashing through the bush, with its white tail flaunted, 

 and under such circumstances the white mark is extremely con- 

 spicuous. 



Indeed, I feel that there is grave ground to question the general 

 statement of Mr. Thayer that " almost all mammals are equipped 

 with a full obliterative shading of surface colours ; that is, they 

 are darkest on the back and lightest on the belly, usually with 

 connected intermediate shades." This is undoubtedly true as a 

 statement of the coloration, but whether this coloration is in 

 fact obliterative needs further investigation. Of course, if it is 

 obliterative, then its use is to conceal the mammals. Mr. Thayer's 



