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. 2018 Apr 16;8:5998. doi: 10.1038/s41598-018-24454-4

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© The Author(s) 2018

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

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Vestiges of pre-Columbian earthworks are still visible today. (a) Accumulations of earthworm casts cover the surfaces of weirs. Vestiges of weirs have been extensively reworked by earthworms, which are attracted to these and other elevated structures during the flooding period. (b,c) Weirs are still visible not only because earthworms continually move soil to them, but also because they harbour taller vegetation (tall grass and woody plants) than the lower-lying floodplain. (d) Aerial photo of four successive V-shaped structures along a weir, showing associated (dry) ponds, and woody vegetation at the point of each V. (e) V-shaped structure seen from the ground, looking downstream, showing trees and dense vegetation growing at the elevated point of the V, and a pond just upstream of the point. (f) Aerial orthophoto of three (dry) ponds, the downstream berm of each of which is colonised by woody vegetation. (g) Ground view of a dry pond. Arrows indicate direction of water flow during the high-water season. Photos (11–17 October 2016): Rumsaïs Blatrix (a–c,e), Bruno Roux (d,f) and Doyle McKey (g).