MONTHLY WILDLIFE RESEARCH LETTER 
Vol, 2, No. 2 
Page 2 
the lens technique for determining the age of rabbits. 
A manuscript was completed concerning the advantages of performing 
roadside censuses for rabbits during the night (rather than the early morning) 
for all but the summer months. Galley proof of another manuscript describing 
the technique of determining the winter mortality of rabbits was received from 
the Journal of Wildlife Management and was corrected and returned for publi¬ 
cation. 
W-55-R-3 - Inactive. F. Bellrose 
W-56-R-3 G. Sanderson, K. Johnson 
Preliminary data were tabulated from X-ray photographs made of the 
radii and ulnae of captive and wild raccoons during 1957 and 1958. Ossa bacula, 
radii, and ulnae from several hundred wild males and radii and ulnae from a 
few hundred females killed during the 1958 hunting season were examined. These 
examinations indicated that the condition epiphyseal cartilage may be used to 
separate male raccoons into two age classes (young-of-the-year and older) during 
the hunting and trapping season in Illinois. Males with broad epiphyses are 
young-of-the-year, those with thin or moderate epiphyses are in the 1 l/2-year 
age class. 
The ossa bacula are still the most convenient method for determining 
the age of males. However, there are a small number of bacula which are inter¬ 
mediate between the young-of-the-year and the adult condition. Previously it 
was not always possible to place them in the correct age group, but this is 
now possible if both baculum and radius and ulna are available. A young-of-the- 
year animal with an intermediate baculum will have broad epiphyses while an 
older animal with an intermediate baculum will have either very thin or completely 
closed epiphyses. Probably the epiphyseal cartilage disappears when males are 
between 13 and 19 months of age. 
Data from females indicate that the time of closing of the epiphyseal 
cartilage is more variable than in males and that it probably occurs somewhat 
later. It appears that the epiphyses in non-parous females close when the 
animals are between 19 and 31 months of age. At this time it is not possible 
to tell when epiphyses close in parous females, but some were at least 39 to 
ii3 months old when their epiphyses closed. Thus, during the hunting season in 
Illinois, females with open epiphyses are young-of-the-year animals or non- 
parous females up to 1 l/2-years old. 
W-61-R-2 F. Greeley, J. Ellis 
The transfer of rural mail carrier township indices to pheasants and 
per cent of soil associations in each township were transferred from IBM cards 
