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Unearthing real-time 3D ant tunneling mechanics

Buarque de Macedo, Robert and Andò, Edward and Joy, Shilpa and Viggiani, Gioacchino and Pal, Raj Kumar and Parker, Joseph and Andrade, José E. (2021) Unearthing real-time 3D ant tunneling mechanics. Proceedings of the National Academy of Sciences of the United States of America, 118 (36). Art. No. e2102267118. ISSN 0027-8424. PMCID PMC8433525. doi:10.1073/pnas.2102267118.

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Granular excavation is the removal of solid, discrete particles from a structure composed of these objects. Efficiently predicting the stability of an excavation during particle removal is an unsolved and highly nonlinear problem, as the movement of each grain is coupled to its neighbors. Despite this, insects such as ants have evolved to be astonishingly proficient excavators, successfully removing grains such that their tunnels are stable. Currently, it is unclear how ants use their limited information about the environment to construct lasting tunnels. We attempt to unearth the ants’ tunneling algorithm by taking three-dimensional (3D) X-ray computed tomographic imaging (XRCT), in real time, of Pogonomyrmex ant tunnel construction. By capturing the location and shape of each grain in the domain, we characterize the relationship between particle properties and ant decision-making within an accurate, virtual recreation of the experiment. We discover that intergranular forces decrease significantly around ant tunnels due to arches forming within the soil. Due to this force relaxation, any grain the ants pick from the tunnel surface will likely be under low stress. Thus, ants avoid removing grains compressed under high forces without needing to be aware of the force network in the surrounding material. Even more, such arches shield tunnels from high forces, providing tunnel robustness. Finally, we observe that ants tend to dig piecewise linearly downward. These results are a step toward understanding granular tunnel stability in heterogeneous 3D systems. We expect that such findings may be leveraged for robotic excavation.

Item Type:Article
Related URLs:
URLURL TypeDescription Information
Buarque de Macedo, Robert0000-0002-2218-4117
Andò, Edward0000-0001-5509-5287
Joy, Shilpa0000-0002-0169-7036
Viggiani, Gioacchino0000-0002-2609-6077
Pal, Raj Kumar0000-0001-5039-7710
Parker, Joseph0000-0001-9598-2454
Andrade, José E.0000-0003-3741-0364
Additional Information:© 2021 National Academy of Sciences. Published under the PNAS license. Edited by David A. Weitz, Harvard University, Cambridge, MA, and approved July 18, 2021 (received for review February 8, 2021). This work was supported by Army Grants W911NF-17-1-0212 and W911NF-19-1-0245. Laboratoire 3SR is part of the Laboratoire d’Excellence Mechanical and Process Engineering supported by Investissements d’Avenir Grant n ANR-11-LABX-0030. Data Availability: Experimental data and code have been deposited in CaltechDATA (code and data for “Unearthing real-time 3D ant tunneling mechanics”; Author contributions: E.A., S.J., G.V., and J.E.A. designed research; R.B., S.J., R.K.P., and J.E.A. performed research; R.B., E.A., G.V., and R.K.P. analyzed data; and R.B. and J.P. wrote the paper. The authors declare no competing interest. This article is a PNAS Direct Submission. This article contains supporting information online at
Funding AgencyGrant Number
Army Research Office (ARO)W911NF-17-1-0212
Army Research Office (ARO)W911NF-19-1-0245
Agence Nationale pour la Recherche (ANR)ANR-11-LABX-0030
Subject Keywords:tunneling; granular mechanics; ants; robotics; applied physical sciences
Issue or Number:36
PubMed Central ID:PMC8433525
Record Number:CaltechAUTHORS:20210824-153629422
Persistent URL:
Official Citation:Unearthing real-time 3D ant tunneling mechanics. Robert Buarque de Macedo, Edward Andò, Shilpa Joy, Gioacchino Viggiani, Raj Kumar Pal, Joseph Parker, José E. Andrade. Proceedings of the National Academy of Sciences Sep 2021, 118 (36) e2102267118; DOI: 10.1073/pnas.2102267118
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110400
Deposited By: Tony Diaz
Deposited On:24 Aug 2021 16:57
Last Modified:22 Nov 2021 23:18

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