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Relation between body-size and thermoregulation behavior: postprandial thermophily in spiny-tailed agama Uromastyx acanthinura Bell

Berec M., Stará Z., Poláková S.

Polish Journal of Ecology

2014

Vol. 62, nr 1

139--145

Ectothermal vertebrates regulate their body temperature within definite limits to maintain physiological processes at their optimal levels. Among others, food processing and absorption are strongly temperature-dependent. Deficiency of adequate temperatures limits ectotherms in growth and maintenance. On the other hand, thermoregulatory behavior is costly and should be constrained by many factors. Using artificial thermal gradients (26–44°C), we measured temperature preferences of 10 spiny-tailed agamas (Uromastyx acanthinura) in controlled indoor experiment. Each lizard could choose place in the terrarium before and after feeding. Then, temperature preferences during pre-feeding and post-feeding periods were compared. We found significant increase of preferred temperature after feeding. Detailed view revealed that there is consistent influence of body size: bigger lizards maintained higher temperature during the whole experiment. We hypothesize that bigger potential predation risk on smaller lizards due to their size would force them to choose less optimal conditions.

Parental provisioning in response to natural variation of brood size in the Black-billed magpie (Pica pica L.) : video analysis of behaviors in the nests

Lee S., Jabłoński P., Choe J., Choi J.

Polish Journal of Ecology

2010

Vol. 58, nr 3

553-562

Natural selection will favor parents who adjust their effort in relation to the fitness costs and benefits from the current brood. In this study, we investigated how magpie parents adjust provisioning effort based on the number of nestlings in the brood, by analyzing video recordings of begging and feeding behaviors of birds. The number of visits per hour increased with brood size, but the number of feeding events per visit did not. Because of the latter, parental provisioning that a nestling is receiving on average decreased in larger broods. This may be viewed either as an evidence for the limitation of parental provisioning in larger broods, or as an evidence of parental strategy optimizing the brood-size-specific provisioning effort for the current reproductive event as a tradeoff between current and future reproduction. With other aspects of parental provisioning behavior, we did not find clear indication that parent confronts upper limitation in provisioning large broods. Pervisit number of feeding and nestlings. body condition around the time of fledging did not depend on brood size, which implies that parental effort is not at its limit in larger broods. Based on the results, we suggest that the provisioning effort of black-billed magpie parents is better explained by the life-history trade-off model for provisioning.