Thermal preferences, metabolic rate, and water flux of the brown treesnake (Boiga irregularis) in the laboratory and on Guam

Ecophysiology is the study of the effects of physiologic attributes and limitations on the interactions between an animal and its environment. Most studies addressing ecophysiology of snakes have been performed in diurnal snakes living in temperate environments. New comparative data for snakes representing diverse habitats, phylogenies and ecologies are essential to understanding the relationship of physiology and body temperature (T_b) to snake ecology and evolution. Brown treesnakes (Boiga irregularis) are tropical, nocturnal, and arboreal colubrid snakes. Given their biology and their abundance on Guam, this species is an excellent candidate to represent an understudied, but common ecotype of snake.; After the introduction, the second chapter finds that in thermal gradients and on Guam, brown treesnakes thermoregulate around two temperature ranges that coincide with smooth (21.3 C to 24.9 C) and plateau (28.1 C to 31.3 C) body temperature (T_b) patterns. In the gradient brown treesnakes choose to elevate T_b in the evening. On Guam snakes are restricted to achieve plateau T_bs only when direct solar radiation is available. Copper model studies indicate that operative temperatures do not vary across refuge types, unless sites receive unshaded solar radiation.; The third chapter uses indirect calorimetry to investigate the effects of temperature on oxygen consumption rate (VO₂), CO₂ production rate (VCO₂), total evaporative water loss (TEWL), and respiratory quotient (RQ) in brown treesnakes. Between 20 C and 30 C VCO ₂, VO₂, TEWL and RQ values are similar to other snakes. VCO ₂ and VO₂ rise markedly between 30 C and 35 C suggesting that brown treesnakes experience thermal stress at 35 C. The chapter presents intraspecific and interspecific allometric equations for VO₂, VCO ₂ and TEWL.; Chapter four validates the doubly labeled water technique (DLWT) in brown treesnakes by comparison with indirect calorimetry and stomach content analysis. The DLWT accurately predicts total water loss in dry and humid conditions. Due to changes of total body water of >12% the DLWT did not provide a precise estimate of metabolic rate under dry conditions in this study. Under humid conditions and on Guam, the DLWT overestimates metabolic rate in brown treesnakes by a factor of 4.6.