68 YEARBOOK, PUBLIC MUSEUM, MILWAUKEE. [Vol. I. 



The following condensed account indicates the methods used in the 

 study, the numlier of remains of each species found, and other informa- 

 tion of general interest. 



The pellets (figure 38-2) were carefully pulled apart with tweezers, 

 and the skulls contained were used for the count and identification. The 

 majority of small mammals can be identified by the skulls if the teeth 

 are present, and this lot, which, due to the season, consisted principally 

 of adults, was over 90% determinable. 



The remains of the White-footed Mice of the subgenus Pcromysciis 

 were somewhat fragmentary, and thanks are due Dr. Wilfred H. Os- 

 good of the Field IMuseum of Chicago, an authority on the group, for 

 examining this part of the material. A specimen of this mouse is shown 

 in figure 38-8. 



As the pellets were broken up somewhat, the number was estimated 

 by weight, ten perfect ones of average size being used as a basis. 



Total number of pellets examined (weight estimate) 407 



Greatest number of skulls found in any one pellet. Common 



Shrew — Sorc.v pcrsonatus 5 



Average number of skulls per pellet Two and a fraction 



Total number of animals whose remains were found 836 



Of the last number 805, or about 96% were mice, 26, or about 3% 

 shrews, 3 birds and 2 crawfish. 



SPECIES REPRESENTED IN THE PELLETS 



Meadow Mouse, Microtus pcnnsylvanicus (figure 38-4) 761 



It will be seen that the great bulk (about 91% ) of the Long-eared Owl's 

 winter food in this locality consisted of these destructive creatures. 

 These mice breed with astonishing rapidity and unless held in check by 

 their natural enemies, of which the Long-eared Owl is one, would soon 

 be numerous enough to do an increcHble amount of damage to crops of 

 various kinds. 



Mice of the subgenus Pcromysciis Gloger 43 



Although Dr. Osgood found much of this material indeterminate as to 

 species, remains of both the Northern White-footed Mouse, Pcrouiyscus 

 leucopus iwz'cbomcciisis (Fischer) and the Prairie White-footed Mouse, 

 Pcromysciis maiiiciilatiis bairdi (Hoy & Kennicott) were identified, the 

 latter being probal^ly the most numerous. Mice of this genus consti- 

 tuted only a trifle over 5% of the total number of creatures eaten. 



