Annual energy budgets of the timber rattlesnake: Advancements, refinements, and open questions

The Timber Rattlesnake (Crotalus horridus) is representative of an extreme low energy, ambush-foraging lifestyle, Several technological advancements and data from long-term studies have enabled a more detailed examination of annual and lifetime energy budgets. Specifically, we draw on a 16-yr laboratory and field study of the physiological ecology of G horrid us to assemble annual and lifetime field energy budgets, Temperature-sensitive radiotelemetry and remote monitoring provide detailed information on field body temperature profiles. Body temperature profiles, coupled with body mass- and season-specific resting metabolic regressions (derived from laboratory studies of metabolism), allow estimation of minimal maintenance budgets, Laboratory feeding studies quantify digestive performance, cost of digestion, and cost of growth, We combine these variables with season-specific measurements of size-specific growth and field metabolism of free-ranging snakes to estimate growth and activity components of energy budgets, Finally, studies of the metabolic cost of vitellogenesis allow a more refined estimate of reproductive effort, which can be summed over different schedules of litter size and frequency, To maintain a life-history phenotype similar to snakes in northwest Arkansas, Timber Rattlesnakes must consume approximately 70% of their body weight per year. We estimated female reproductive effort to range between 27% and 32% of total annual energy budget Recurrent themes in C, lwrridus energy budgets include the high degree of inter-annual and inter-individual variation in constituent variables which reduce precision and extreme behavioral and physiological flexibility, reflective of their adaptation to low-energy boom-or-bust lifestyles.