THE GRAY SQUIRREL 
TEADILY the forests have been felled, 
and with them the gray squirrels have 
gradually disappeared, until their num- 
bers have so decreased that for a hundred and fifty 
years there has not occurred one of those great 
squirrel migrations so common in the United States 
during the time of the early settlers. Guided by 
an impulse still unfathomed by naturalists, the 
squirrels congregated in vast armies and marched 
across the country. The distance over which they 
moved was largely governed by the obstacles which 
they encountered—trivers, lakes, and mountains. The 
climatic conditions and the food supply by the way, 
according as they were favorable or unfavorable, 
lengthened or shortened these migrations. As the 
squirrels pushed blindly forward, thousands upon 
thousands perished by the way, and the survivors 
gradually spread over a great territory, until lost in 
the vast wilderness. 
Years might elapse before another great migration 
133 
