SUMNEB — DESEKT AND LAVA-DWELLING MICE 
75 
DESERT AND LAVA-DWELLING MICE, AND THE PROBLEM 
OF PROTECTIVE COLORATION IN MAMMALS 
By Fkancis B. Sumneb 
[Plate 6] 
The prevailing tendency of desert animals — particularly the mam- 
mals, birds and reptiles — to assume a buff or pallid hue is a phenom- 
enon which has long attracted the attention of naturahsts. In many 
cases these colors harmonize strikingly with those of the bare sand and 
gravel, as well as with the commonly parched and stunted vegetation 
amid which such animals dwell. Oftentimes the creature need only 
come to rest in order to disappear from view, its presence becoming 
evident only when running or flying is resumed. 
At a first glance it would seem perfectly evident that we here have to 
do with the well-known phenomenon of concealing coloration. This, 
we might suppose, has been acquired by these various creatures through 
the process of natural selection. The vegetable feeders among them 
have become more and more invisible to their carnivorous pursuers, 
while the latter have profited in being concealed from their prey. It 
is commonly assumed by those who hold this view that the color varia- 
tions which are selected for survival are quite random in. their origin, 
at least to the extent that they are not influenced in any direct way by 
the environment. 
Various facts make it evident that this explanation is quite inade- 
quate in the case at hand. I will mention but a few of the more obvi- 
ous objections here. Later, I shall discuss certain special lines of 
evidence, based upon my own field and laboratory observations. 
(1) Most desert rodents are strictly nocturnal in their habits. (This, 
admittedly, is not a conclusive argument, since the moonlight of the 
desert is brilliantly clear, and it is probable that owls, at least, among 
the predators, are largely guided in their search for prey by sight.) 
(2) One group of these rodents — the pocket gophers — spend practi- 
cally their whole time beneath the ground. Nevertheless, strikingly 
pale species are to be found in certain desert regions. (Here again, 
it must be admitted that carnivorous animals, both birds and mam- 
mals, lay a heavy toll upon the gophers, catching them frequently when 
they are half emerged from their holes.) 
(3) The process of depigmentation apphes to parts of the body 
which are not exposed to view. For example, the soles of the feet of 
