Abstract:
I conducted three experiments to compare metabolic and digestive parameters of Cope's Gray Treefrogs, Hyla chrysoscelis. I monitored oxygen consumption (V02) rates of fasted and fed treefrogs (n = 8) in 4-h intervals over 24-h to determine if higher levels of resting V02occurred at night during the species' normal activity period. There were no significant differences among V02 values at different times of day (P = 0.33), and no interaction between time of day and treatment group (P = 0.50). However, there was a highly significant difference (P < 0.0001) in V02 between fasted and fed animals, with fed animals having V02 rates 2.6 to 4.1 times higher than fasted animals. I measured the food passage time (FPT) of eight H. chrysoscelis at 24 C and six at 16 C to determine the effect of temperature on FPT. I fed adult male treefrogs a meal of a single marked cricket for four consecutive nights. I measured the amount of time between ingestion of marked food and defecation of each marker. All treefrogs ate marked crickets at 24 C, but only six treefrogs ate marked crickets at 16 C. Means ± SD of FPTs were 91.1 ± 29.2 h at 16 C and 38.2 ± 9.76 h at 24 C (P = 0.006). I fed 11 male H. ch,ysoscelis single crickets once daily at 2000 h for eight days to determine digestive efficiency. I dried fecal samples at 70 C and combusted with a Parr Instrument Company oxygen bomb calorimeter. The mean ± SD apparent digestibility coefficient for H. chrysoscelis was
81.1 ± 3.8%. Linear regression showed a positive linear relationship between calories consumed and calories in feces (~ = 0.76, P = 0.0006). Low resting metabolic rate, short FPT, and efficient digestion at 20 to 24 C correspond with the species' life history patterns.
