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The Thermal Dependence of Feeding Behaviour, Food Consumption and Gut-Passage Time in the Lizard Lacerta vivipara Jacquin
R. Van Damme, D. Bauwens and R. F. Verheyen
Vol. 5, No. 4 (1991), pp. 507-517
Published by: British Ecological Society
Stable URL: http://www.jstor.org/stable/2389633
Page Count: 11
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Although the effects of temperature on ectotherm physiology have been generally recognized, consequences for animal performance in the field have seldom been assessed. We experimentally investigated the thermal dependence within the body temperature range 20-35⚬C, of distinct behavioural and physiological functions related to feeding (sprint speed, prey-catching rate, prey-handling rate, gut-passage rate, voluntary food intake, mass change) in the lizard Lacerta vivipara Jacquin. All functions examined were strongly dependent on body temperature (Tb); their rate generally increased rapidly within the range 20-30⚬C and then levelled. Exceptions were gut-passage rate and the amount of weight change, which exhibited a decline at 35⚬C. Some small but consistent differences in thermal sensitivities between performance functions were evident. Gut-passage rate and weight change were maximal at Tb ≈ 30⚬C, which is slightly lower than the optimal temperature of the other functions (32-34⚬C). Passage rate had the widest, whereas prey-catching rate and weight change had the narrowest 80% thermal performance breadth. These results indicate that no single Tb maximizes all behavioural and physiological processes and therefore supports the `multiple optima' hypothesis. We predicted performance levels in the field by integrating results of the thermal sensitivity experiments with data on Tbs of field-active L. vivipara. Lizards seem to be able to achieve >80% of their maximum capacity for most of the time, at least during sunny weather. Under cloudy/variable conditions, when lizards suffer impaired possibilities to thermoregulate, performance levels were reduced. This depression is less accentuated for gut-throughput rate and weight change. We discuss our results in the context of the overall thermal biology of this cool-climate lizard.
Functional Ecology © 1991 British Ecological Society