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Edward M. Lunk 
cottontails, but did not present substantiating data on total fat or 
other physical condition. 
The objectives of my study were (1) to identify a postulated 
relationship between a morphometric measure of body size and total 
body fat in cottontails and (2) to develop a field index for body 
condition of live cottontails. I present preliminary evidence that a 
massdength ratio was significantly correlated with total body fat in 
a small sample of cottontails in North Carolina. I also discuss de- 
velopment of a field index using mass/head-length as a predictor of 
the percentage of total body fat, an indicator of body condition. 
METHODS 
During April 1984 12 cottontails were trapped or shot from 
three different study sites in the North Carolina Piedmont. Total 
length (nose tip to tail tip) was measured with a tape; head length 
(nose tip to back of skull at posterior edge of lambdoidal crest) 
was measured with calipers. Animals were weighed with a spring 
scale and were frozen within 4 hours for later laboratory analysis. 
When collected, two of the heaviest animals, collared as part of an 
earlier telemetry study, had skin lesions caused by the collars, and 
had dropped in rank to second and third lowest in terms of crude 
fat. These values were retained in the analysis. 
Frozen cottontails were weighted with a Mettler digital bal- 
ance. I used frozen masses obtained on the digital balance in pref- 
erence to fresh masses obtained with a spring balance because of 
the greater precision of the former and later determination that the 
spring scale might have been unreliable. Specimens were homog- 
enized before assay of crude fat. In preparation for homogenizing, 
hair was shaved to avoid clogging the homogenizer, carcasses were 
sliced laterally, and digestive tracts were cleaned. Animals were au- 
toclaved for 30 minutes to soften tissues and masticated with a 
laboratory homogenizer (Janke & Kunkel IKA Werk Ultra-Turrax 
Type T45-S4). Homogenate from each animal (500-600 mL) was 
dried for 4 days in a ventilated oven and was stirred twice daily 
to break up crust and to promote drying. Triplicate 2-g samples 
were weighed and oven-dried for 5 hours for percentage of dry- 
mass determination. Triplicate 2-g samples were weighted into ex- 
traction crucibles for determination of ether extract (Pickel extraction 
of crude fat) expressed as a percentage of ovendried tissue mass. 
Because of the small sample size I investigated relationships 
between body measurements and total fat with single dependent variable 
models for both sexes combined. A natural log transformation nor- 
malized the distribution of fat content as shown by normal prob- 
ability plots and the Shapiro-Wilk W-test (SAS Institute, Inc. 1990) 
