Thermal influences on foraging ability: body size, posture and cooling rate of an ambush predator, the python Morelia spilota

Abstract

Summary 1.The interface between thermal biology and foraging mode has attracted little scientific attention, but may be crucially important to the biology of ectothermic predators. Slip & Shine (1988c) suggested that the ability of large heavy-bodied snakes to ambush nocturnally active mammals relied on the snakes' control of cooling rates through their thermal inertia (via body size and postural adjustments) and microhabitat selection. 2. We tested assumptions underlying this hypothesis, using Diamond Pythons (Morelia s. spilota) from southeastern New South Wales. Our laboratory studies confirmed that larger body sizes and coiled postures significantly retarded cooling rates, and that body temperature affected the snakes' ability to detect potential prey items. 3. The magnitude of these effects on cooling rates was great enough to extend the time period substantially over which an adult Diamond Python, lying in ambush in a suitable microhabitat, would be able to detect and capture nocturnally active prey. For example, the times taken for pythons to reach thermal equilibration under our experimental conditions (cooling from 33 to 12°C) were < 1 h for hatchling pythons regardless of posture, 1 h for outstretched juveniles, 2 h for coiled juveniles and outstretched adults, and almost 8 h for coiled adults. 4. The high rates of cooling of juvenile pythons, even when they are tightly coiled, may force them to rely upon diurnally active prey rather than crepuscular or nocturnal species.

An experimental study of the effects of weed invasion on lizard phenotypes

“…For example, a shortterm consequence of suboptimal body temperatures could be reduced activity (Bennett 1983), and consequently a reduction in food intake or rates of feeding (e.g. Ayers and Shine 1997). Continuously reduced thermoregulatory opportunities may lead to slower rates of growth (Downes and Bauwens 2004;Dawson et al 2005), and decreased fecundity (Downes 2001;Karlsson and Wiklund 2005).…”

CONVERGENT EVOLUTION OF EMBRYONIC GROWTH AND DEVELOPMENT IN THE EASTERN FENCE LIZARD (SCELOPORUS UNDULATUS)

“…Daily and seasonal patterns of environmental temperature affect profiles of body temperatures in both thermoregulators and thermoconformers. Consequently, thermal environments determine the duration and effectiveness of foraging (Grant and Dunham 1990;Ayers and Shine 1997;Wapstra and Swain 2001), consumption and assimilation (Ji et al 1995;Kingsolver and Woods 1997;Angilletta 2001). These thermal constraints on behavioral and physiological processes generate latitudinal and altitudinal variation in the growth, development, and maturation of ectotherms (Beaupre 1995;Niewiarowski 2001;Sears and Angilletta 2004).…”

Temperature-Dependent Sex Determination in Vertebrates

“…However, growth rate (usually measured by change in dry mass) is not a single variable; it is influenced by innumerable behavioral, physiological, and morphological variables that may be individually influenced by temperature. For example, expedited growth at increased temperatures may be linked to increased appetite (Greenwald 1974;Lang 1979), increased prey capture and handling ability (Avery et al 1982;Van Damme et al 1991), and/or increased foraging efficiency (Avery et al 1982; Ayers and Shine 1997;Greenwald 1974). Nevertheless, warm temperatures are most often reported to be positively correlated with growth rates (Brett 1971;Elliott 1982;Lillywhite et al 1973;Mrosovsky 1980;Van Damme et al 1991).…”