Vo 1. 14, No. 5 
Page 4 
correlated with ambient temperature. The relationship is given in the 
equation Y = 0.079 - 0.00044X for the caged cottontails, and Y = 0.105 
- 0.00037X for those in the pens, when X is the air temperature and Y 
is the number of grams of rabbit chow consumed daily per gram of body 
weight. 
The inverse relationship between energy utilization by the rabbits 
and air temperature probably results from the decreasing requirements 
of energy for thermoregulation by homoiothermic animals as the zone of 
thermoneutrality (the range of temperatures at which no energy is ex¬ 
pended for maintenance of body temperature) is approached. The correla¬ 
tion between energy consumption and ambient temperature appears to be 
closer if the data from the spring of the year are excluded, which sug¬ 
gests the influence of endocrine changes associated with the breeding 
season, or that full acclimation to the summer temperatures may be slow. 
The greater energy utilization by the cottontails in the pens than 
by the caged rabbits may reflect the greater activity by the penned 
rabbits, compared with the more confined rabbits in the cages. Thus, 
estimates of energy consumption by penned rabbits should better approxi¬ 
mate the energy comsumption of free-ranging cottontails. 
