120 FIELD MUSEUM OF NATURAL HISTORY ZOOLOGY, VOL. XL 



conditions. Considering the great abundance of these animals in 

 early days, we may well suppose that in poor "nut years" the scarcity 

 of their favorite food would supply a sufficient cause; and assuming 

 scarcity of food to be the dominant factor governing such concerted 

 movements among these animals, the absence of such migrations at 

 the present day may readily be explained on account of the enormous 

 decrease in numbers of Squirrels and consequent abundance of nuts, 

 even in poor years, for those that remain. 



Kennicott says, "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 

 abundant as before. I am not aware that they ever migrate except 

 when exceedingly abundant. Of these immense hordes, but few 

 probably survive. No sudden 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 as has 

 been stated; 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 mammals, 

 all of which feast when the squirrels migrate. I learn from Dr. Hoy, 

 that one of these migrations is said to have taken place in southern 

 Wisconsin in 1842; he witnessed another in 1847, and a third in 1852. 

 From these facts, and from observations 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 migra- 

 tions observed by him in southern Wisconsin occurred when the mast 

 was exceedingly abundant and the squirrels in excellent condition. 

 Near Racine, they were observed passing southward in very large 

 numbers for about two weeks, at the end of September and the begin- 

 ning of October; and it was a month before all had passed. They 

 moved along leisurely, stopping to feed in the fields, and upon the 



* It is interesting to note that Dr. Hoy's prediction that Gray Squirrels would 

 migrate in Wisconsin in 1857 was fulfilled. In a letter to Mr. A. W. Bray ton, written 

 at Racine, April 2, 1878, he says, "Black and Gray Squirrels did migrate in 1857 as 

 predicted. Whether there is a precise interval between these 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 I could not determine whether there was an 

 attempt to migrate or not, as they are nearly exterminated now in this vicinity. 

 In 1857 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 afternoon. In other years one might stand at the same 

 place six months and not see one individual." (Bray ton, Geol. Surv. Ohio, IV, 

 1882, p. in, foot note.) 



