Body size affects digestive performance in a mediterranean lizard

P. Pafilis, S. Meiri, K. Sagonas, D. Karakasi, E. Kourelou, E. D. Valakos

Research output: Contribution to journalArticlepeer-review

Abstract

Effective digestion is decisive for survival. In nature, where most animals feed sporadically, high digestive performance guarantees they will gain the most out of their infrequent meals. Larger body size implies higher energy requirements and digestion should function properly to provide this extra energy. Comparing Skyros wall lizards (Podarcis gaigeae) from Skyros Island to large (“giant”) lizards from a nearby islet, we tested the hypothesis that digestion in large individuals is more efficient than in small individuals. We anticipated that giant lizards would have higher gut passage time (GPT), longer gastrointestinal (GI) tracts and higher apparent digestive efficiencies (ADE) for lipids, sugars and proteins. These predictions were only partially verified. Giant lizards indeed had longer (than expected based on body length) GI tract and longer GPTs but achieved higher ADE only for proteins, while ADEs for lipids and sugars did not differ from the normal-sized lizards. We postulated that the observed deviations from the typical digestive pattern are explained by cannibalism being more prominent on the islet. Giant lizards regularly consume tail fragments of their conspecifics and even entire juveniles. To break down their hard-to-digest vertebrate prey, they need to extend GPT and thus they have developed a longer GI tract. Also, to fuel tail regeneration they have to raise ADEproteins. It seems that larger size, through the evolution of longer GI tract, enables giant lizards to take advantage of tails lost in agonistic encounters as a valuable food source.

Original languageEnglish
Pages (from-to)199-205
Number of pages7
JournalHerpetological Journal
Volume26
Issue number3
StatePublished - Jul 2016

Keywords

  • Body size
  • Cannibalism
  • Digestion
  • Gigantism
  • Islands
  • Reptiles

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