Meeting Abstract

41.2  Tuesday, Jan. 5  Long-Term Studies of Field Metabolic Rate in Timber Rattlesnakes (Crotalus horridus): Annual Variation, Critical Factors, and Implications for Bioenergetic Studies. BEAUPRE, Steven J.; University of Arkansas, Fayetteville sbeaupre@uark.edu

Mechanistic studies of bioenergetics are critical to developing a predictive understanding of organismal responses to environmental change. Field metabolic rate (FMR) integrates energetic expenditures due to maintenance, biochemical activity, and physical activity. As such, field metabolic rates constitute an important response that provides insight regarding ecological factors that influence the mass-energy flux of individuals. I used the doubly-labeled water method to measure FMR in a large sample of radio-tagged Timber Rattlesnakes (Crotalus horridus) at a long-term study site in Northwest Arkansas. One hundred and ninety-five measurements of FMR were made among 59 individuals during the active season (May-September) over nine years (1996 to 2004 inclusive). FMR scaled allometrically with body mass following 0.477W^1.13. Water efflux and influx were nearly isometrically related to body mass. Significant variation in the magnitude of FMR was apparent among years and among seasons (spring-summer transition, summer, and summer-fall transition). Supplemental feeding of experimental snakes increased FMR by a factor of two over naturally foraging (control) snakes. No effects of sex or ecdysis were apparent. High variability in observed FMR of Timber Rattlesnakes, especially with respect to annual variation, elicits caution when interpreting scaling relationships based on small samples from geographically focused and temporally limited studies. Mass scaling exponents that exceed 1.0 have been previously reported among snakes and have potentially important implications for estimation of field energy budgets and interpretation of factors that influence FMR.