2. A graph based on weights of raccoons of known 
ages was constructed. Weights on the graph were used 
as guides for estimating the ages of wild raccoons 
weighing less than 7 pounds. 
3. X-ray photographs were made of the radii and 
ulnae of raccoons of known ages. Photographs showing 
the condition of the epiphyses (broad, thin, or closed) 
were used as guides for aging wild raccoons, both male 
and female, live and dead. 
4. Penis bones of dead males of known ages were 
collected and studied. Size and degree of ossification of 
these bones were used as guides for aging wild raccoons. 
5. The average date of birth calculated for raccoons 
in the wild was used to arbitrarily assign an age to a 
raccoon found by X-ray of epiphyseal cartilage or other 
aging method to be a juvenile where (1) the body 
weight was not available, (2) the animal weighed more 
than 7 pounds, or (3) the animal was caught after 
November 1. The average date of birth for 17 litters 
conceived in the wild in the northern half of Illinois 
was April 16; the earliest date was March 9, the latest 
June 10. 
6. No significant weight differences were found be- 
tween males and females of the same ages, even though 
birth weights and growth rates differed among  indi- 
viduals. 
7. Thirty-five of 35 intact male raccoons with broad 
epiphyses were 15 months of age or less; 14 (82 per 
cent) of 17 males with thin epiphyses were 13-19 
months of age. Eleven of 13 males (85 per cent) with 
closed epiphyses were 16-21 months of age. 
8. Forty-four of 45 intact female raccoons with 
broad epiphyses were 15 months of age or less; 14 (61 
per cent) of 23 females with thin epiphyses were 14-19 
months of age, and | with thin epiphyses was 31 months 
of age. Six females 19-30 months of age had closed 
LITERATURE CITED 
Hale, James B. 
1949. Aging cottontail rabbits by bone growth. Jour. Wildlife Mgt. 13(2):216—25. 
Hamilton, W. J., Jr. 
1936. The food and breeding habits of the raccoon. Ohio Jour. Sci. 36:131—40. 
Llewellyn, Leonard M. 
1953. Growth rate of the raccoon fetus. Jour. Wildlife Mgt. 17(3):320-1. 
Petrides, George A. 
1959. Age ratios in raccoons. Jour. Mammal. 40(2):249. 
Rinker, George C. 
1944. Os clitoridis from the raccoon. Jour. Mammal. 25(1) :91-2. 
Sanderson, Glen C. 
1950. Methods of measuring productivity in raccoons. Jour. Wildlife Mgt. 14(4):389-402. 
Sanderson, Glen C. 
1961. The lens as an indicator of age in the raccoon. Am. Midland Nat. 65(2):481-5. 
epiphyses. In two additional females the epiphyses 
closed when one was a minimum of 39 months and the 
second a minimum of 42 months of age. 
9. The condition of epiphyses during the hunting 
and trapping season in Illinois was found to furnish an 
adequate means for separating raccoons, both males 
and females, living and dead, into two age groups, 
juveniles and adults. 
10. The size and condition of penis bones, as de- 
scribed in a previous study, were found useful in dis- 
tinguishing juveniles from adults in dead males. 
11. Castration of young males resulted in relatively 
slow growth and abnormal development of the bacula 
due to lack of the male sex hormone and appeared to 
have a slight effect on the age at which the epiphyses 
closed. The effect of castration on the baculum was first 
apparent when an animal was between 7 and 10 months 
of age. 
12. A method of aging described several years ago 
and based upon whether the penis can be easily ex- 
truded through the preputial orifice was still found to 
be useful in distinguishing adults from juveniles in liv- 
ing and dead males during the hunting and trapping 
season. ; 
13. All parous females examined during the hunting 
and trapping season in Illinois were adults. 
14. Seven females which would have been classified 
as parous on the basis of the nipples alone had no 
placental scars. These were probably animals which 
became pseudopregnant during the first mating season 
following their birth. 
15. Although the epiphyseal plates were found to 
provide a useful method for aging both male and female 
raccoons, living and dead, in all but a few cases classi- 
fication to juvenile and adult in dead males can be 
more easily accomplished by examining the bacula. 
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