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‘The reason for these migrations is not satisfactorily explained. That 
they are caused by want of food is hardly probable, as the squirrels are 
found to be fat at the time, and as often leave localities abounding with 
food as otherwise, After one of these grand migrations, very few of the 
species are found in the localities from which they have moved, and 
these, as if alarmed at the unusual solitude, are silent and shy. They 
rapidly increase in numbers, however, and in a few years are as abun- 
dant as before. I am not aware that they ever migrate except when 
exceedingly abundant. Of these immense hordes but few probably sur- 
vive. Nosudden increase in their numbers was heard of in southern 
Wisconsin after the several migrations from northern Illinois. Many 
are drowned in attempting to cross streams; not a few are destroyed by 
man; some die from utter exhaustion, and when forced to travel in an. 
unnatural manner, upon the ground, they fall an easy prey to rapacious 
birds and mammais, all of which feast when the squirrels migrate.” 
I learn from Dr. Hoy that one of tnese migrations is said to have 
taken place in 1842; he witnessed another in 1847, and a third in 1852. 
From these facts, and from cbservations made in Ohio and elsewhere, he 
is of the opinion that the migrations, in most cases at least, occur at 
intervals of five years; and if he be right, the squirrels, which are now 
exceedingly abundant again in southern Wisconsin, may be expected to 
migrate in the autumn of 1857.* He further says that the migrations 
observed by him in southern Wisconsin occurred when the mast was 
exceedingly abundant and the squirrels in good condition. Near Racine 
they were observed passing southward in very large numbers for about 
two weeks, at the end of September and the beginning of October, and 
it was a month before all had passed. They moved along rather leis- 
urely, stopping to feed in the fields, and upon the abundant nuts and 
acorns of the forests. So far had they departed from their accustomed 
habits that they were seen on the prairie, four or five miles from any 
timber; but even there, as usual, they disliked to travel on the ground, 
and ran along the fences wherever it was possible. 
* Since writing the above I have received the following letter from Dr. Hoy: | 
RACINE, April 2, 1878, 
DEAR SiR: Black and gray squirrels did migrate in 1857, as predicted. Whether 
there is a precise interval between their migrations I will not pretend to state, yet they 
did migrate in this section in 1847, 1852, and 1857, since which they have become so 
scarce that 1 could not determine whether there was an attempt to migrate or not, as 
they are nearly exterminated now in this vicinity. In 1457 I knew one negro who stood 
by a tree, in an open space on the line of a fence, and shot over twenty in one after- 
noon. In other years one might stand at the same place six months and not see one 
individual, Yours, P. R. Hoy. 
