Thermoregulation is of great importance for the survival and fitness of ectotherms as physiological functions are optimized within a narrow range of body temperature (T(b)). The precision with which reptiles thermoregulate has been proposed to be related to the thermal quality of their environments. Although a number of studies have looked at the effect of thermal constraints imposed by diel, seasonal and altitudinal variation on thermoregulatory strategies, few have addressed this question in a laboratory setting. We conducted a laboratory experiment to test whether tuatara, Sphenodon punctatus (order Rhynchocephalia), a cold-adapted reptile endemic to New Zealand, modify their thermoregulatory behaviour in response to different thermal environments. We provided tuatara with three thermal treatments: high-quality habitat [preferred T(b) (T(sel)) could be reached for 8 h/day], medium-quality habitat (T(sel) available for 5 h/day) and low-quality habitat (T(sel) available for 3 h/day). All groups maintained body mass, but tuatara in the low-quality habitat thermoregulated more accurately and tended to maintain higher T (b)s than tuatara in the high-quality habitat. This study thus provides experimental evidence that reptiles are capable of adjusting their thermoregulatory behaviour in response to different thermal constraints. This result also has implications for the conservation of tuatara. A proposed translocation from their current habitat to a higher latitudinal range within New Zealand (similar to the shift from our 8 h/day to our 5 h/day regime) is unlikely to induce thermoconformity; rather, tuatara will probably engage in more effective thermoregulatory behaviour.
Animal species diff er considerably in their response to predation risks. Interspecifi c variability in prey behaviour and morphology can alter cascading eff ects of predators on ecosystem structure and functioning. We tested whether speciesspecifi c morphological defenses may aff ect responses of leaf litter consuming invertebrate prey to sit-and-wait predators, the odonate Cordulegaster boltonii larvae, in aquatic food webs. Partly or completely blocking the predator mouthparts (mandibles and/or extensible labium), thus eliminating consumptive (i.e. lethal) predator eff ects, we created a gradient of predator-prey interaction intensities (no predator Ͻ predator -no attack Ͻ predator -non-lethal attacks Ͻ lethal predator). A fi eld experiment was fi rst used to assess both consumptive and non-consumptive predator eff ects on leaf litter decomposition and prey abundances. Laboratory microcosms were then used to examine behavioural responses of armored and non-armored prey to predation risk and their consequences on litter decomposition. Results show that armored and non-armored prey responded to both acute (predator -non-lethal attacks) and chronic (predator -no attack) predation risks. Acute predation risk had stronger eff ects on litter decomposition, prey feeding rate and prey habitat use than predator presence alone (chronic predation risk). Predator presence induced a reduction in feeding activity (i.e. resource consumption) of both prey types but a shift to predator-free habitat patches in non-armored detritivores only. Non-consumptive predator eff ects on prey subsequently decreased litter decomposition rate. Species-specifi c prey morphological defenses and behaviour should thus be considered when studying non-consumptive predator eff ects on prey community structure and ecosystem functioning.
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