Contrasts in energy intake and expenditure in sit-and-wait and widely foraging lizards

Abstract

Daily energy metabolism and water flux were measured with doubly labeled water in the free-living insectivorous lizards Cnemidophorus tigris (mean body mass 15.7 g) and Callisaurus draconoides (8.6 g) in June 1979 in the Colorado Desert of California. C. tigris was an active forager; it spent 91% of its 5-h daily activity period in movement. C. draconoides was a sit-and-wait predator; it spent less than 2% of its 10-h activity period in movement. C. tigris had significantly higher rates of field energy metabolism and water influx (210 Jg day, 36.8 ul HO g day, N=19) than C. draconoides (136, 17.1, N=18). There were no significant differences between the sexes within either species.The extra costs of free existence were calculated from differences between field metabolic rates and maintenance costs estimated from laboratory respirometry. Rates of energy metabolism during the field activity period were about 1.5x resting levels at 40° C (∼field active body temperature) for C. draconoides and 3.3 x resting levels at 40° C (∼field active body temperature) for the more active C. tigris. Feeding rates calculated from water influx data were 13.3 mg g day for C. tigris and 5.8 mg g day for C. draconoides. Though C. tigris had a high rate of energy expenditure, its foraging efficiency [Formula: see text] was higher than C. draconoides'.

The correlated evolution of biomechanics, gait and foraging mode in lizards

“…Second, the cost of locomotion during walking has been shown to be greater than running, both on a per stride basis and on an absolute basis, because WF actually spend the majority of their activity budget walking slowly (Anderson and Karasov, 1981;. Thus, it is difficult to support the idea that walking mechanics is a key adaptive innovation to reduce the metabolic cost of locomotion in WF.…”

Locomotor performance of closely relatedTropidurusspecies:relationships with physiological parameters and ecological divergence

“…For example, an increase in proportion of fast-glycolytic fibers associated with high limb cycle frequency appears to enhance sprint speed in phrynosomatid species that locomote on sand (Bonine et al, 2001). Improved endurance capacity, involved in the large distances covered by lizards that forage actively, is associated with high proportions of oxidative fibers in the leg muscles (Mutungi, 1992), high field metabolic rates (Anderson and Karasov, 1981) and high metabolic scopes (Frappell et al, 2002). Muscle fibers of a glycolytic nature contract quickly but fatigue rapidly, whereas slow-oxidative fibers, aerobic in nature, exhibit high endurance (Brooks et al, 1996) but require improved oxygen delivery to the muscle.…”

Energetic costs of activity by lizards in the field

“…The TRM for an ectothermic animal incorporates the energy expenditure of a resting animal with the daily body temperature pattern found in animals in the field (Anderson & Karasov 1981;Congdon & Tinkle 1982;Peterson, Nagy & Diamond 1990;Benabib & Congdon 1992). Although %AR is a more aggregated index than ECT, and therefore provides less detailed information about the subdivision of an animal's energy budget, it is easier to obtain because it does not require direct measurements of time, distance travelled and/or energy expended in locomotion.…”

“…The lizard studies that have subdivided the total daily energy expenditure into its components have demonstrated that widely foraging species have higher %ARs than sit-and-wait foragers (Anderson & Karasov 1981;Nagy, Huey & Bennett 1984) and that the proportion of energy used in activity (as well as the daily total) can change seasonally (Alexander & Whitford 1968;Merker & Nagy 1984;Christian & Tracy 1985;Mautz & Nagy 1987;Christian & Weavers 1994;Christian et al 1995;Christian, Griffiths & Bedford 1996a;Christian et al 1996b,c).…”