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Preest, M.R. and F.H. Pough. 2003. Effects of body temperature and hydration state on organismal performance of toads, Bufo americanus. Physiological and Biochemical Zoology 76: 229-239. Full Article

Temperature and humidity are dominant environmental variables affecting performance of nocturnal, terrestrial amphibians. Toads are frequently active at body temperatures (Tb) and hydration states (HS) that yield suboptimal performance. We investigated the combined effects of Tb and HS on feeding, locomotion, and metabolism of Bufo americanus. More toads responded to the presence of prey when fully hydrated than when dehydrated, and times to orient to prey, maneuver around a barrier, and reach prey were less in hydrated than in dehydrated animals. Time to capture prey decreased with increasing Tb in fully hydrated, but not dehydrated, toads, and hydrated animals caught prey more rapidly than did dehydrated animals. Distance traveled in 5 min and aerobic scope were affected by Tb. Generally, individuals that performed well in the feeding experiments at a particular Tb and HS also performed well at a different Tb and HS. The same was true for distance traveled and aerobic scope. However, within combinations of Tb and HS, correlations between performance variables were minimal. Specialization of a particular variable resulting in high performance at a certain Tb and HS does not appear to exact a cost in terms of performance at a different Tb and HS.

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