MAMMALS OF PENNSYLVANIA AND NEW JERSEY. 55 



may be added that the midday summer temperature of these deforested 

 subcanadian areas where the blacks were once so numerous is greatly in- 

 creased above that of primeaval conditions and may have been the cause of 

 mortality among them, the greater exposure to the sum being much more 

 detrimental to a black animal than a gray one. In regard to the second 

 theory it may be also said that the natural enemies of the black squirrel would 

 derive the same peculiar advantage in its capture through deforestation 

 and consequent exposure as would man himself. In a word, the original 

 status of the black gray squirrel is dependent on an environment combining 

 the climate and flora of the Upper Transition and Lower Canadian life zones, 

 in which coniferous and nut-bearing trees were normally in the proportion of 

 about ten to one. As these conditions through human agency revert to those 

 of the Lower Transition and Upper Austral zones, with a corresponding 

 increase in population, the ratio of blacks to grays decreases. 



Historic references. — " Squirrels came down [into the lowlands] from the 

 higher countries into [eastern] Pennsylvania at certain seasons. The inhabi- 

 tants attribute this to the coming of a rigorous winter." — Kalm's Travels, p. 

 316. Kalm does not share this opinion, as the year he was in Pa. (autumn 

 of 1749) when such a migration took place, it was a mild winter. He thinks 

 it caused by the scarcity of nuts in one place and their abundance in another. 

 On page 320 he says that from January, 1749, to January, 1750, Pennsylvania 

 paid bounties to lessen the squirrel pest at the rate of 3 pence a head ; 8,000 

 being so paid ! The bounty was then reduced one-half. See also, Watson's 

 Annals, in which both gray and black squirrels are mentioned. In Ord's 

 Zoology (Guthrie's Geography, 2nd Amer. Ed., 1815, p. 292) he names the 

 black phase of Gray Squirrel as " Small Black Squirrel, Sciurus pennsylvanica" 

 and in a foot note he says, "This has always been confounded with the fore- 

 going [gray squirrel] , but it is a different species. It abounds in those parts 

 of Pennsylvania which lie to the westward of the Allegheny ridge."* This is 

 of interest as showing that in the early part of the nineteenth century the 

 black squirrel was, as now, more typical of northwestern Pa. than of any other 

 part of the state. On the same page Ord describes and names the " New 

 Jersey Squirrel Sciurus hiemalis" from Tuckerton, as being distinguished by 

 its " bearded ears." This name is a synonym of carolinensis. 



Description of Species. — From the common tawny colored gray squirrel of 

 the south Atlantic lowlands, the northern form leucotis is distinguished by 

 greater size and a purer gray or silvery color at all seasons, not intermixed or 

 tipped above with reddish or tawny as in carolinensis. Largest individuals 

 often approach the fox squirrel in size, being 2 to 3 inches longer than full 



* Ord's name being earlier than leucotis would have held good for the northern gray 

 squirrel had he given a description of it. Lacking this, it has no place in nomenclature. 



