Jan., 1913 
CONCEALING AND REVEALING COLORATION OF ANIMALS 
9 
iikely to survive, and the others to perish. Another species may be varying in 
the direction of revealing coloration, but at the same time developing some other 
element of safety which far outweighs the disadvantage of revealing coloration, 
and thus would survive. Most naturalists who have studied the two in the field 
will probably agree that the crow, whose color under most circumstances cannot 
he considered at all concealing-, is, because of its intelligence, alertness and ac- 
tivity, quite as capal)le of escaping its natural enemies, armed onlv with natural 
weapons, as is the ptarmigan, which affords one of the best examples of conceal- 
ing coloration. 
The law of compensation runs all through nature, animate as well as inani- 
mate, and cannot be ignored by naturalists. In the natural course of things, a 
more or less revealingly colored animal would be expected to develop its alert- 
ness, speed or some other factor of safety, to a greater extent than its better-con- 
cealed neighbor. In fact, this seems to be the actual result in certain familiar 
cases, though not at all in other instances, so far as we ma}" jivlge. There is some 
reason for the supposition that reliance upon concealment in many cases enables 
an enemy to approach very closely before escape is attempted. Thus conceal- 
ing coloration, reacting upon mental and physical activity, may possibly some- 
times be an actual disadvantage, if its concealing effect be known to its possessor, 
of which we cannot very well be certain until we can persuade the animals to 
tell us. 
It is possible, if not probable, that many other causes besides the need of con- 
cealment contribute to the coloration of animals. Mr. Beebe’s experiments upon 
the direct effect of moisture, dryness, heat, cold, diet, etc., upon animal colors are 
well known and enlightening, whatever the final conclusions may be. Some other 
facts bearing upon this phase of the problem, generally known to professional 
zoologists, are often ignored, and may not be so well known to amateurs. For 
example: (a) The general possession of dark skins by tropical animals, which is 
not confined to tropical human beings and which is ])OSsibly not due merely to 
the direct blackening of the skin by the sun (“tanning”), but to pigmentation for 
protection of the living tissues from the destructive action of intense light, ex- 
cessive heat, or both, (b) The difference between different colors in their power 
to radiate heat, which may rec[uire animals of different habitat to be differently 
colored without reference to concealment. Thus such colors would be protective, 
yet not concealing. “Protection” is a broader term than “concealment,” and 
the two should not l)e used synonymously, (c) The difficulties found in attempting 
to introduce white-skinned animals (swine) into certain regions, which may be 
due to the deleterious effect of intense light, (d) The difference in the color of 
domestic horses under different climatic conditions, possibly due to temperature 
or light, or moisture, a matter now under inve.stigation. Professor Chas. F. 
Woodruff has recently discussed this subject {Scioice, n. s., xxxv, April 12, 1912, 
pp. 591-593). The recent change of color of the linnet introduced into Hawaii 
may be due to some such cause. 
If no animal were in need of concealment, it is probable that species would 
still differ in color and color pattern. Among the smaller animals many species 
differ minutely in color and color pattern, yet so slightly that the differences are 
.scarcely discernible, except by direct comparison, with specimens in hand. These 
differences can hardly be for concealment. Sometimes colors are the result nf 
refraction of light due to physical structure, as in pearls, opals and iridescent 
feathers of birds. Sometimes they are the result of chemical composition, as in 
rubies, emeralds, sandstones, limestones, etc. In the cases just mentioned, except 
