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Edited by Simon A. Levin, Princeton University, Princeton, NJ, and approved December 17, 2018 (received for review November 7, 2018)
Significance
Termite mounds are the result of the collective behavior of termites working to modify their physical environment, which in turn affects their behavior. During mound construction, environmental factors such as heat flow and gas exchange affect the building behavior of termites, and the resulting change in mound geometry in turn modifies the response of the internal mound environment to external thermal oscillations. Our study highlights the principles of self-organized animal architecture driven by the coupling of environmental physics to organismal behavior and might serve as a natural inspiration for the design of sustainable human architectures.
Abstract
Several species of millimetric-sized termites across Africa, Asia, Australia, and South America collectively construct large, meter-sized, porous mound structures that serve to regulate mound temperature, humidity, and gas concentrations. These mounds display varied yet distinctive morphologies that range widely in size and shape. To explain this morphological diversity, we introduce a mathematical model that couples environmental physics to insect behavior: The advection and diffusion of heat and pheromones through a porous medium are modified by the mound geometry and, in turn, modify that geometry through a minimal characterization of termite behavior. Our model captures the range of naturally observed mound shapes in terms of a minimal set of dimensionless parameters and makes testable hypotheses for the response of mound morphology to external temperature oscillations and internal odors. Our approach also suggests mechanisms by which evolutionary changes in odor production rate and construction behavior coupled to simple physical laws can alter the characteristic mound morphology of termites.
Footnotes
↵1S.A.O. and A.H. contributed equally to this work.
- ↵2To whom correspondence should be addressed. Email: lmahadev{at}g.harvard.edu.
Author contributions: S.A.O., A.H., and L.M. designed research, performed research, analyzed data, and wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1818759116/-/DCSupplemental.
Published under the PNAS license.
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Morphogenesis of termite mounds
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