Size matters to lizards, but numbers may not

wall lizard

Tests in Italian ruin or wall lizards suggests that the reptiles can assess dinner based on volume differences between two food ideas but not on the number of food items available.

pjt56/Wikimedia Commons (CC BY-SA 3.0)

The quantitative abilities of lizards may have their limits.

From horses to salamanders, lots of different species display some form of number sense, but the phenomenon hasn’t been investigated in reptiles. So a team of researchers in Italy set up two experiments for 27 ruin lizards (Podarcis sicula) collected from walls on the University of Ferrara’s campus. In the first test, the team served up two house fly larvae of varying sizes. Lizards consistently chose to scarf down bigger maggots.

Then in the second experiment, the researchers gave lizards a choice between different numbers of larvae that were all the same size. The lizards didn’t show a preference. While the data suggest that the reptiles do discriminate between larger and smaller prey, they don’t distinguish between higher and lower numbers of maggots in a meal, the scientists report April 12 in Biology Letters.

The researchers cite two potential explanations for the discrepancy. Selecting larger prey rather than more prey might sometimes be advantageous for a predator. Or reptiles simply lack the numerical know-how seen in vertebrate relatives, such as fish.

Editor’s note: This story was updated April 17, 2017, to replace the previous image of a Podarcis muralis lizard with one that shows P. sicula, the species used in the study.

Helen Thompson is the multimedia editor. She has undergraduate degrees in biology and English from Trinity University and a master’s degree in science writing from Johns Hopkins University.

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