. Bulletin. Natural history; Natural history. 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 st
. Bulletin. Natural history; Natural history. 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 per cent of all fox squirrels, and 39, or per cent of all gray squirrels
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