522 



Illinois Natural History Survey Bulletin 



Vol. 23, Art. 





it. Removal of hedgerows, which has 

 been extensive during recent years, has 

 measurablj' reduced the acreage of habit- 

 able fox squirrel range in the state. 



Undoubtedly the best hedgerow cover 

 for squirrels is offered by very large, un- 

 trimmed Osage orange trees, but a hedge 

 of this size lowers the crop yield for a 

 distance of 20 or 30 feet on each side and 

 therefore is resented, with some justifi- 

 cation, by many landowners. Smaller 

 hedgerows are of material value to fox 

 squirrels, and trimming, although it im- 

 pairs, does not destroy their usefulness to 

 squirrels. Fencerows of oaks, elms, 

 maples, hickories or red cedars are com- 

 monly used by fox squirrels to the limit of 

 food and cover offered. 



The value, to fox squirrels particularly, 

 of one or a few good food trees in hedge- 

 rows, corners or in open stands is appre- 

 ciable. The most desirable species for 

 such situations are hickories, including 

 pecans, walnuts and most oaks. They are 

 well adapted to hedgerow planting, as they 

 produce well when isolated and thus fa- 

 vored by full light. 



Den Boxes. — Den boxes, fig. 40, suit- 

 able for squirrels and other cavity nesting 

 species have been tested extensively in 

 Illinois (Hawkins & Bellrose 1941, Hes- 

 selschwerdt 1942, Yeager 1942, Brown & 

 Bellrose 1943) and in Michigan (Allen 

 1942, 1943). The outcome of these 

 studies leaves little doubt of the possibility 

 of substituting artificial for natural cavi- 

 ties in regions where the latter are scarce 

 or lacking. Den boxes appear to be es- 

 pecially useful on the black prairie, where 

 the shortage of natural cavities is acute, 

 and in food-producing forest stands too 

 immature for cavity formation. 



Almost any covered box or keg having 

 an entrance hole and room for a nest will 

 be used by squirrels if placed in a tree on 

 their range. The box recommended here 

 is 2 feet deep, 8 by 8 inches inside cross 

 section, and with an entrance hole 3 inches 

 in diameter. It should have a removable 

 top to facilitate cleaning, which is oc- 

 casionally necessary because squirrels fill 

 boxes with leaves and other materials. 

 Small cracks in the boxes do not seem to 

 interfere wnth use of the box by squirrels, 

 and a perch will be used if present but is 

 not necessary. Boxes constructed from 

 nail kegs or sound old lumber will last 



Fig. 40. — Two types of artificial den boxes 

 suitable for squirrels. A box having a mini- 

 mum cross section of 8X8 inches, at least 2 

 feet deep and with an entrance 3 inches in 

 diameter, is recommended. 



for 2 or 3 years or longer. Such boxes 

 can be built and erected for a small sum 

 each ; if made of cypress or cedar lumber 

 that must be purchased as new, the cost 

 will be higher. However, nests made of 

 the better material will give, with some 

 repair, at least 10 years of service. Two 

 or three boxes per acre are ample, and they 

 should be placed in the larger trees, 20 

 feet or more above ground. In order to 

 insure the most effective utilization, they 

 should not be placed in den trees, but in- 

 stead in sound trees some distance away 

 from den trees. On large tracts, boxes 

 placed on or near the timber edge are more 

 attractive, at least to fox squirrels, than 

 those 100 yards or more inside the stand. 

 Where ample tree cavities already exist, 

 it is a waste of time and materials to in- 

 stall artificial dens, and for this reason 

 their use in most all-age stands is unnec- 

 essary. 



Control of Fire and Grazing. — The 

 burning and grazing of woodlands in Illi- 



