PROTF.CTIVE ('OT.ORATION 507 



whole thesis is that such is the case. But as a matter of tact, the 

 great majority of these mammals, when they seek to escape 

 observation, crouch on the grounti, and in that postuae the light 

 belly escapes observation, and the animaPs colour pattern loses 

 very much of, and sometimes all of, the " full obliterative shading 

 of surface colours^' of which Mr. 'J'hayer speaks. Moreover, when 

 crouched down in seeking to escape observation, the foes of the 

 animal are most apt to see it from above, not from below or from 

 one side. This is also the case with carnivorous animals which 

 seek to escape the observation of their prey. The cougar crouches 

 when lying in wait or stalking, so that it is precisely when it is 

 seeking to escape observation that its lighter-coloured under parts 

 are obscured, and the supposed benefit of the " obliterative shading 

 pattern " lost. I do not intend without qualification to take 

 ground one way or the other on this general question ; but it is 

 certainly true that any such sweeping statement as that (juoted 

 above by Mr. Thayer is as yet entirely unproved. I have no doubt 

 that in most cases animals whose colours harmonize with their 

 environment, and which also seek to escape observation by remain- 

 ing motionless when they think there is danger, are very materially 

 helped by their concealing coloration ; but when this concealment 

 is said to be due to the obliterative shading as described by 

 Mr. Thayer, it is certainly worth while considering the fact that 

 the so-called obliterative j)attern is least shown, or is not shown at 

 all, at the only time when the animal seeks to escape observation, 

 or succeeds in escaping observation — that is, when it crouches 

 motionless, or skulks slowly, with the conscious aim of not being 

 seen. No colour scheme whatever is of much avail to animals 

 when they move, unless the movement is very slow and cautious; 

 rats, mice, gophers, rabbits, shrews, and the enormous majority ot 

 mammals which are coloured in this fashion are not helped by their 

 special coloration pattern at all when they are in motion. Against 

 birds of prey they are practically never helped by the counter- 

 shading, but merely by the general coloration and by absence of 

 movement. Their chief destroyers among mammals — such as 

 weasels, for instance — hunt them almost or altogether purely by 

 scent, and though the final pounce is usually guided by sight, it is 

 made from a distance so small that, as far as we can tell by 

 observation, the " counter-shading '' is useless as a protection. In 

 fact, while the general shading of these small mammals"' coats may 

 very probably protect them from certain foes, it is as yet an open 

 question as to just how far they are helped (and indeed in very 

 many cases whether they really are helped to any appreciable 

 extent) by what Mr. Thayer lays such special stress upon as being 

 " full obliterative shading (counter-shading) of surface colouring." 

 Certainly nmny of the markings of mammals, just as is the case 



