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Digging the optimum pit: Antlions, spirals and spontaneous stratification

Franks, Nigel R.; Worley, Alan; Falkenberg, Max; Sendova-Franks, Ana B.; Christensen, Kim

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Nigel R. Franks

Alan Worley

Max Falkenberg

Ana Sendova-Franks
Associate Professor in Biometry & Animal Behaviour

Kim Christensen


Most animal traps are constructed from self-secreted silk, so antlions are rare among trap builders because they use only materials found in the environment. We show how antlions exploit the properties of the substrate to produce very effective structures in the minimum amount of time. Our modelling demonstrates how antlions: (i) exploit self-stratification in granular media differentially to expose deleterious large grains at the bottom of the construction trench where they can be ejected preferentially, and (ii) minimize completion time by spiral rather than central digging. Both phenomena are confirmed by our experiments. Spiral digging saves time because it enables the antlion to eject material initially from the periphery of the pit where it is less likely to topple back into the centre. As a result, antlions can produce their pits—lined almost exclusively with small slippery grains to maximize powerful avalanches and hence prey capture—much more quickly than if they simply dig at the pit’s centre. Our demonstration, for the first time to our knowledge, of an animal using self-stratification in granular media exemplifies the sophistication of extended phenotypes even if they are only formed from material found in the animal’s environment.


Franks, N. R., Worley, A., Falkenberg, M., Sendova-Franks, A. B., & Christensen, K. (2019). Digging the optimum pit: Antlions, spirals and spontaneous stratification. Proceedings of the Royal Society B: Biological Sciences, 286(1899), 20190365.

Journal Article Type Article
Acceptance Date Mar 4, 2019
Publication Date Mar 27, 2019
Deposit Date Mar 27, 2019
Publicly Available Date Mar 27, 2019
Journal Proceedings of the Royal Society B
Print ISSN 1471-2954
Electronic ISSN 1471-2954
Publisher Royal Society, The
Peer Reviewed Peer Reviewed
Volume 286
Issue 1899
Pages 20190365
Keywords animal traps, spontaneous stratification, granular materials, optimized construction, self-organization, extended phenotype
Public URL
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Related Public URLs dryad.k7m5vf4
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