Effects of Body Mass and Temperature on Standard Metabolic Rate in the Eastern Diamondback Rattlesnake (Crotalus adamanteus)

Determining the consequences of body size and body temperature (T_b) variation is critical to understanding many aspects of snake ecology, because size and temperature play such important roles in the biology of ectotherms. Here, we investigate the effects of body size and temperature variation on the energetics of the largest species of rattlesnake, the Eastern Diamondback Rattlesnake (Crotalus adamanteus). Specifically, we measured oxygen consumption to estimate the standard metabolic rate (SMR) of five C. adamanteus (mass range 800–4980 g) at 5-degree increments from 5–35 C. A multiple regression model indicated that SMR increased with body size and temperature. Q₁₀s were generally high (range 1.82–4.20) compared to other squamates but were similar to the high values calculated for other large rattlesnakes. An energy balance model for C. adamanteus predicted that as T_b increases, so must prey consumption to meet annual SMR energy demands. Thus, T_b variation likely affects patterns of energy acquisition and use and, in turn, influences processes such as growth and reproduction.

Fig. 1.

Examples of oxygen consumption (ml O₂/h) measurements of Crotalus adamanteus measured at 25 C using a computer-controlled, open-flow respirometry system, which sampled every 24 min. Note the sporadic activity exhibited by most snakes, as well as the differential ability of the two estimation techniques (average [dashed line] vs lower quartile [solid line]) to reduce the influence of elevated VO₂ rates from SMR estimates. Time zero equals 0915 h

Fig. 2.

Relationship between SMR and body mass in five Crotalus adamanteus at seven experimental temperatures. Each symbol represents a different temperature. At all temperatures, body mass significantly affected SMR (mean R² = 0.91, range = 0.79–0.98; all P-values < 0.05)

Fig. 3.

Residual log₁₀ VO₂ (adjusted for body mass) of Crotalus adamanteus at temperatures ranging from 5–35 C. To obtain residuals, all log₁₀-transformed mass and SMR data were combined into a single linear regression model. Values are presented as mean ± 1 SE

Contributor Notes

(MED) Department of Biology, Davidson College, Davidson, North Carolina 28035; and (WAH, JHR) University of Georgia's Savannah River Ecology Laboratory, Drawer E, Aiken, South Carolina 29803. (MED)midorcas@davidson.edu; (WAH)hopkins@srel.edu; and (JHR)roe@srel.edu Send reprint requests to MED.

Accepted: 01 Oct 2003