Vol. J4, No. 1 
Page 4 
to 22.5 to 30.5 percent for the 1963-64, 1965 - 67 , and 1968-70 periods, 
respectively. 
Thus, the increased level of hatching success, coupled with the 
increasing proportion of hens at Bogota that are nesting on the sanctuaries, 
where hatching success is particularly high (67 percent, 8-year mean), 
has played the major role in the recent encouraging increases in the 
population level. The increasing level of nest predation indicates that 
nature's culling agents now have a greater chance at nests that used to fall 
victim to plows and hay mowers. 
6. Rabbit Management G. B. Rose 
The energy consumed per day by cottontail rabbits in outdoor pens 
and in outdoor cages was measured as described in MWRL 13(2):4-5, from 
February through December 1970» Food consumed per day by the rabbits was 
negatively correlated with air temperature, for both the rabbits in the pens 
and the rabbits in the cages. The relationship for the caged rabbits was 
expressed^by the equation Y=90»8-0.42X, and for the penned rabbits by the 
equation Y=119.1—0.40X, when X is the mean air temperature for the experimental 
period, and Y is the number of grams of rabbit chow consumed per rabbit 
per day. 
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 expended 
for maintenance of body temperature) is approached. 
The greater energy utilization by the rabbits in the pens than by the 
caged rabbits may reflect the greater activity by the penned rabbits than 
by the more confined rabbits in the cages. 
