MAMMALS OF PENNSYLVANIA AND NEW JERSEY. IO7 



Distribution in Pa, and N. y. — Not found in Pa. In N. J. confined 

 closely to sphagnum bogs in the cedar swamp belt. 



History, habits, etc. — The air of mystery surrounding the discovery of 

 Cooper's mouse and the long period elapsing after Baird's announcement of 

 it before any specimens were secured east of the Alleghany mountains have 

 made its history peculiar. Another notable thing about it is the fact that it 

 reproduces or rather extends into the austral zone a type of mouse life which 

 had heretofore been considered peculiar to an Arctic climate. Even in the 

 present day with improved methods and knowledge of mouse trapping it is 

 rarely caught, and certainly seems to be very rare compared with its abund- 

 ant associates, and allies, the meadow and woodland voles of the genera 

 Microtus and Evotomys. Stone's lemming was first trapped in the deep 

 sphagnum surrounding a small open pool or spring of water near the edge of 

 the big dam at May's Landing. A cedar swamp was near by on one side and 

 the pine barren woods nearly cast a shade over it next to the pond. Not five 

 feet from the same spot Mr. Stone caught his new wood vole, Evotomys, 

 while we were here on a previous visit. Specimens of both novelties were 

 taken later in the same place, and, as will be noted, several others have been 

 secured in other parts of N. J. Of the habits of this lemming we are quite 

 ignorant from observation of the living animal. The places where I have 

 found true cooperi in the east have never been in woodland, but generally 

 swampy mountain clearings near woods among dense grass and weeds, and 

 appearing to use the same paths as the common meadow mouse. By setting 

 traps in these you generally have to thin out the meadow mice before a 

 Synaptomys will have a chance to be caught, ratio of the two being as i to 30 

 in favor of Microtus. Undoubtedly swamp grasses and succulent weeds such 

 as we know to form the main food of Microtus are the lemming's chief diet 

 also. The same remarks apply to Stone's lemming, only it keeps more 

 closely to the sphagnum beds where there is no need for it to expose itself to 

 the sun and heat of a warmer clime. In these places it acts as a sort of go- 

 between for Microtus and Evotomys, yet it is more essentially Microtine in 

 its associations here also, and frequent are the trapper's disappointments to 

 find so many lemming-like captures turn out to be voles when their long tails 

 come to view. I have never found the nest of Synapto?nys, but Quick and 

 Butler (Amer. Nat., 1885, p. 114) describe it as "always under cover, gen- 

 erally in a hollow log or stump and composed of fine grass. It is not so 

 securely built as the nests of some of the other species of this family." An- 

 other peculiar circumstance in regard to Cooper's lemming is the difference 

 of its chosen habitat in the Ohio Valley from what we find east of the Alle- 

 ghanies. I took a specimen in spring, 1898, on a high, dry, rocky hillside 

 pasture among grass and stump land about a mile from the town of Beaver, 

 Pa. A large colony of M. pennsylvanicus lived on this hillside, but this was 



