470 



ILLINOIS Natural History Survey Bulletin 



Vol. 23, Art. 5 



weight, representing gains in weight of 

 about ZZ or more per cent since July. 



Development of summer or second-litter 

 juveniles approximated that of spring or 

 first-litter young in both species, and, as 

 would be expected, summer-born animals 

 taken the following September and Oc- 

 tober showed the lowest average weight 

 of any age class in the kill at that time. 



Length 



Body and total lengths of 706 fox squir- 

 rels and 317 gray squirrels were recorded, 

 table 10. All readings were taken in 

 a standard manner (Anderson 1932). 

 Length of the hind foot was taken for a 

 large series, but the differences appeared 

 so insignificant that taking of this meas- 

 urement was discontinued. 



Spring juveniles were first collected in 

 May, at which time the average body 

 length and total length in the fox squirrels 

 were 231 millimeters and 461 millimeters, 

 respectively, and, in the gray squirrels, 205 

 millimeters and 389 millimeters, re- 

 spectively, table 10. By mid fall these 

 measurements had increased, respectively, 

 about 17 and 13 per cent in fox squirrels, 

 and about 27 and 21 per cent in gray 

 squirrels. The apparently greater rate 

 of increase in gray squirrels may be ac- 

 counted for by the 2-week difference in 

 the average breeding dates of the two 

 species, and, consequently, in the propor- 

 tionally 3-ounger age of gray squirrels 

 collected in May. 



Summer juvenile fox squirrels, first col- 

 lected in August, had an average body 

 length of 236 millimeters at the time, and 

 267 millimeters in December. Summer 

 juvenile gray squirrels were first collected 

 in September. At that time their average 

 body length was 209 millimeters. In 

 December it was 245 millimeters. 



Deformities 



Only one type of deformity, that of stub 

 tail, was noted in 706 fox squirrels and 317 

 gray squirrels handled by the writers. 

 Ninety-five, or 13.5 per cent of all fox 

 squirrels, and 39, or 12.3 per cent of all 

 gray squirrels, showed this defect to a 

 greater or less degree. This incidence of 

 stub tail in the two species is considered 

 surprisingly high. The deformity is well 



known to hunters, who commonly attrib- 

 ute it to fighting between males and the 

 mating chase between males and females. 

 We have no more logical explanation. In 

 no case was the deformity observed to im- 

 pede travel or any other activity. 



Wounds 



Six crippled squirrels, four fox and two 

 gray, were collected by the writers. 



Fig- 7. — Crippled female fox squirrel col- 

 lected in Piatt County, February, 1945. The 

 injufy was probably caused by a steel trap or 

 a .22 caliber bullet. Despite the injury and 

 a case of mange, this female was pregnant 

 and in good condition as to body fat. 



