Daily Energy Expenditure in Free-ranging Gopher Tortoises (Gopherus Polyphemus)

Energy and Water Flux during Terrestrial Estivation and Overland Movement in a Freshwater Turtle

“…Water influx and efflux rates of 38-41 mL (kg d) Ϫ1 during this period were nearly double those predicted for other reptiles from arid and semiarid regions but in line with those from the tropics (Nagy 1982). FMR and water flux of turtles moving 23 m d Ϫ1 were 46-48 kJ (kg d) Ϫ1 and 22 mL (kg d) Ϫ1 , respectively, both of which are similar to those for active box turtles and gopher tortoises (Table 4; Penick et al 2002;Jodice et al 2006) and consistent with water flux for other nontropical reptiles (Nagy 1982). However, as was the case for estivation, overland movement must be supported by stored energy reserves that cannot be replenished until returning to water, whereas hydration levels can be more easily maintained.…”

“…The development of the doubly labeled water (DLW) technique (Lifson and McClintock 1966) has revolutionized the study of energy and water relations in animals (Nagy et al 1999;Butler et al 2004). Reptiles have proved to be tractable for the DLW method, but studies of turtles are limited to three terrestrial species and two sea turtles (Nagy and Medica 1986;Peterson 1996b;Henen 1997;Penick 2002;Wallace et al 2005;Clusella Trullas et al 2006;Jodice et al 2006). The overall bias against turtles is puzzling, for most can be easily tracked and recaptured, and their ecology and life history has been otherwise well documented within a theoretical framework of energy and water that could be greatly advanced by field studies Mautz 1982;Minnich 1982;Congdon 1989).…”

“…Our inability to detect a mass effect for whole-body rate functions is not completely unexpected because small sample size, mass range, and behavioral variation among individuals often hide any underlying mass effects in field studies (Peterson 1996b). As a result, we used allometric relationships between FMR and water flux rates for reptiles in general because there is insufficient data for turtles alone (but see Jodice et al 2006). The mass exponent for FMR in reptiles is 0.89 (Nagy et al 1999), and for water flux in nontropical habitats, it is 0.91 (Nagy 1982).…”

Total body water and water turnover rates in the estuarine diamondback terrapin (Malaclemys terrapin) during the transition from dormancy to activity

“…2 H, 3 H, DLW) to investigate water relations and energetics of free-ranging animals has increased remarkably, providing valuable insight into body fluid dynamics and water budgets and of animals under natural conditions (Jones et al, 2009). Establishing proper protocols for isotope studies conducted with aquatic ectothermic vertebrates is difficult because of the high water turnover rates (Booth, 2002) and the pronounced seasonal changes in behavior and physiology they undergo (Jodice et al, 2006). Our study has established the first field-based labeled water protocols for diamondback terrapins and helped to provide a better understanding of the terrapin's ability to exploit dynamic and high salinity environments via behavioral and physiological adjustments.…”

“…Total body water and rates of water turnover for animals in a natural environment may be assessed using the stable isotope [ 2 H]deuterium (Nagy, 1989;Speakman, 1997;Jones et al, 2009 Total body water and water turnover rates in the estuarine diamondback terrapin (Malaclemys terrapin) during the transition from dormancy to activity to the environment via evaporation, excretion and salt gland secretion (Jones et al, 2009). Deuterium has been used with success to determine water flux for several species of terrestrial chelonians (Nagy and Medica, 1986;Peterson, 1996;Henen, 1997;Penick et al, 2002;Jodice et al, 2006) and marine turtles (Oritz et al, 2000;Wallace et al, 2005;Southwood et al, 2006;Clusella Trullas et al, 2006;Jones et al, 2009); however, there have been very few studies on freshwater and/or semi-aquatic chelonians (Booth, 2002;Roe et al, 2008).…”