eal plates in the radii and those in the ulnae of indi- 
vidual animals were, with a few exceptions, at similar 
stages of development. Two animals were found in 
which epiphyses of the radii were closed, but those of 
the ulnae were thin. In another animal, the epiphyseal 
plates in the ulnae closed before closure occurred in the 
radii. 
After the epiphyseal plates close in raccoons they 
remain closed. This was indicated in several captives 
of both sexes which were maintained in captivity up to 
more than 2 years after their epiphyseal plates had 
closed. Repeated X-rays of the same animals indicated 
that castration, various hormone treatments, and preg- 
nancy caused no noticeable differences in the epiphyseal 
plates after they were closed. 
Age Estimation by Sexual Characters. — Although 
penis bones may usually be used during the hunting 
and trapping season to classify males as juveniles or 
adults (Sanderson 1950:392), a small percentage of 
bacula at this season are intermediate between the 
\. 
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juvenile and the adult condition. More of these inter- 
mediate bacula were seen in some years than in others, 
the number perhaps depending partly on how early the 
litters were born. For example, for the 1957-58 hunting 
and trapping season, 95 of 3,466 bacula examined, or 
nearly 3 per cent, were classified as intermediate. In 
1958-59, 178 of 3,174, or nearly 6 per cent, and in 
1959-60, 175 of 4,577 bacula, or nearly 4 per cent, 
were Classified as intermediate. Because the writer has 
had considerable experience using bacula for aging 
raccoons and has intermediate bacula from both adults 
and juvenile raccoons of known ages available for com- 
parison, only 19 of these 10,197 bones, or approximately 
0.2 per cent, could not be classified as to age. As a 
rule, bacula classified as intermediate in age are more 
porous at the base if from juveniles, fig. 3 (No. 207), 
than if from adults, fig. 3 (Nos. 121 and 219): 
does not show well in photographs, 
Wild male No. 121 was approximately 19 months of 
age when killed, but the conformation of his baculum. 
porosity 
Fig. 5.— Bacula from raccoons 8 to 11 months of age showing the effects of age and castration on development. Grid 
Squares represent one-half inch. All bacula except Nos. 207 and 308 are of the juvenile type. 
No. 145: captive, estimated 8 months old. 
No. 189: wild, estimated 8 months old. 
No, 270: wild, estimated 8 months old. 
No, 194: wild, estimated 9 months old. 
No. 147: wild, estimated 9 months old. 
No. 279: captive, estimated 9.5 months old. 
No. 207: captive, estimated 10 months old, intermediate- 
type baculum. 
No. 209: captive, estimated 10 months old, castrated. 
No. 308: captive, estimated 11 months old, adult-type 
baculum; reared as a pet until 5 months of age. 
