20 
JOURNAL OF MAMMALOGY 
times we have, when attending at night to some such activity as fumi- 
gation, encountered lone animals meandering about through the trees 
and far from any possible burrow. Nor have I taken into account 
those animals found on the move during the monthly irrigation, for 
then they are flooded out and will make for the nearest dry ground. 
On my ranch near Calexico, Imperial County, California, the pale 
Thomomys perpallidus albatus is abundant, but in this locality the 
gophers live only in the banks of the larger irrigation ditches, where 
they are at all times out of reach of flooding. They never enter the 
fields for more than a few feet, for in summer these are thoroughly 
irrigated at least every ten days and sometimes oftener. My foreman 
is occupied with irrigating a great deal during the night, and he informs 
me that he often finds gophers wandering about well away from bur- 
rows, and in situations that would preclude the possibility that they 
had been flooded out. 
The habit of albatus in apparently instinctively shunning ground 
that will shortly be flooded is worth noting in comparison with that of 
the Covina animal, which latter will readily seek the lowest spots, from 
which they are regularly driven by water. Under original conditions, 
pallescens was never troubled by too much water, except in very rare 
conditions, as when a cloudburst would drive a few unlucky animals 
onto higher ground. On the other hand, albatus was originally con- 
fined to the bottom lands along the lower Colorado River. At stages 
of low water the most attractive habitat was undoubtedly the lower 
association close to the river, as the herbage there would be of a more 
luxuriant character. However, such animals as obeyed this urge would 
invariably be flooded out and drowned by the annual high water con- 
ditions. Hence, along the river, they seem to be, or rather, they were, 
a number of years ago, found only in those situations that are seldom 
or never subject to such perils. In the recent extension of range of 
these animals into the Imperial Valley, their movements are appar- 
ently actuated by the same caution in regard to water. Call it in- 
stinct or what you will. 
It is well known that pocket gophers will make excursions of several 
feet from their burrows, even in the daytime, after especially attrac- 
tive food, but they usually prefer to burrow under their larder, and 
will thus hollow out a large squash or pumpkin from beneath, leaving 
no external signs of the depredation. Very young animals are some- 
times observed sunning themselves near the entrances to the tunnels 
in the most unconcerned manner, but such actions are probably due 
more to curiosity than to anything else. 
