PHYSIOLOGICAL STUDIES OF THE RUFFED GROUSE 



761 



or decreases, both rale of heart and breathing are accelerated or retarded. Because of the 

 great degree of interdependence among these physiologic variables* it may be safely concluded 

 that rate of heart beat per minute and body temperature are fundamentally significant as in- 

 dices of the level of vitality. Respiration rate per minute is a factor of less importance as 

 an index of metabolism, especially for the type of experiment described here. Under other 

 experimental circumstances, for example where an excessive change in body temperature oc- 

 curred, there might be pronounced changes in rate of breathing. 



Resistance to Starvation 



Experiment 6 was devised for measuring the resistance of ruffed grouse to starvation using 

 rectal temperature and respiration rate as indices. 



First, all food except water was withdrawn over a 10-day period from 12 grouse, six of 

 which (Group A) were held at 6.5°F. and six (Group B) at 40°F. throughout the test. Records 

 of rectal temperature and respiration were taken three times daily — morning, afternoon and 

 midnight. A summation of the data for each of these time intervals is presented in table 10}'. 



TABLE 108. EFFECT OF STARVATION WITH WATER AVAILABLE UPON Till'; KICCTVl 



TEMPERATURE OF ADULT GROUSE 



Of interest to the game manager is the greater drop in the level of rectal temperature for 

 fasting birds at midnight compared with that of well-fed birds at the same hour ( Experiment 

 2, figures 83 and 84). During the night there is a natural rhythmical lowering of metabolic 

 activity and external physical movement. Also between midnight and dawn under outdoor 

 conditions the lowest air temperatures usually occur. As the air becomes colder, however, 

 the metabolic rate would tend to increase in order to prevent a drop in body temperature. 

 Under such conditions a fasting bird would have greater difficulty in preventing an excessive 

 reduction of body temperature than would a well-fed bird. 



The difference between the averages of data obtained at 40°F. and 65°F. shows that there 

 was a high physiological correlation between body temperature and environmental tempera- 

 ture at these levels. The smaller standard error for females at 65°F. indicates less variability 

 in their temperature than in that of males at the same air temperature. At 40° F. the degree 

 of variability apparently was not significant between the sexes. 



* As indicated by the highly BigniBcant, positive multiple cone 



+ 0.60 ± 0.165 



