Trenches reduce crop foraging by elephants: Lessons from Kibale National Park, Uganda for elephant conservation in densely settled rural landscapes

PLOS ONE RESEARCH ARTICLE Trenches reduce crop foraging by elephants: Lessons from Kibale National Park, Uganda for elephant conservation in densely settled rural landscapes Allison Rogers ID1*, Adrian Treves1, Richard Karamagi2, Moses Nyakoojo2, Lisa Naughton-Treves3 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 1 Nelson Institute for Environmental Studies, University of Wisconsin-Madison, Madison, Wisconsin, United States of America, 2 Kiko Town Council, Kabarole, Uganda, 3 Department of Geography, University of Wisconsin-Madison, Madison, Wisconsin, United States of America * Abstract OPEN ACCESS Citation: Rogers A, Treves A, Karamagi R, Nyakoojo M, Naughton-Treves L (2023) Trenches reduce crop foraging by elephants: Lessons from Kibale National Park, Uganda for elephant conservation in densely settled rural landscapes. PLoS ONE 18(7): e0288115. https://doi.org/ 10.1371/journal.pone.0288115 Editor: Tunira Bhadauria, Feroze Gandhi Degree College, INDIA Received: December 15, 2022 Accepted: June 20, 2023 Published: July 26, 2023 Copyright: © 2023 Rogers et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Analysis files and R code are also located within the Supporting Information files. Funding: The project was supported by the National Geographic Society through the Early Career Grant awarded to AR [grant number EC68072R-20] (https://www.nationalgeographic.org/ society/grants-and-investments/). AR also received funding from the University of Wisconsin-Madison Crop loss to wildlife, particularly elephants, threatens livelihoods and support for conservation around many protected areas in Africa and Asia. Low-cost elephant barriers have been successfully deployed in savannas but seldom tested around isolated forest parks where the stakes are high for local farmers and isolated elephant populations. We measured the effectiveness of a series of �3 m deep trenches dug by farmers neighboring Kibale National Park, Uganda. We monitored trench quality and crop loss to elephants weekly for a year across 47 transects in four park-adjacent communities, and conducted controlled, beforeand-after comparisons of verified damage. Elephants damaged or destroyed >4 ha of crops during 48 independent foraging events, the majority <220m from the forest boundary. The frequency of damage varied significantly between and within communities. The majority of trenches were not breached by elephants but five suffered �4 breaches. Elephant-breached trenches and their neighboring trenches were lower quality than those not breached in the same week (Wilcoxon test: p<0.001). Trenches were also more likely to be breached where people had planted more crops favored by elephants (Wilcoxon test: p = 0.014). Thus, trench quality and the draw of palatable crops both appeared to influence elephant damage. Although trenches may deter elephants, challenges include heavy labor and difficulties of digging in rocky and swampy areas. Trenches alone will not prevent conflict but this strategy holds promise for hot-spots of conflict at forest edges. Given the stakes for farmers and biodiversity, we call for systematic assessment of crop losses and offer recommendations on monitoring and analysis. Such data will allow for stronger inference about effectiveness before investment of effort and resources in interventions. Introduction Human-wildlife conflict (HWC) around some protected areas threatens local livelihoods and support for conservation. The stakes are particularly high in densely-settled parts of Africa PLOS ONE | https://doi.org/10.1371/journal.pone.0288115 July 26, 2023 1 / 16 PLOS ONE Institute for Regional and International Studies (https://iris.wisc.edu/funding/campus-units/ incoming-grad-awards/). LNT received support from the Mary Herman Rubinstein Fund of the University of Wisconsin-Madison College of Letters and Sciences (https://ls.wisc.edu/news/pioneeringspirit). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. Treves discloses no competing interests but offers a list of funding sources since 2007 and CV for all potential nonfinancial competing interests related to work outside of his institution: All funding awarded to Adrian Treves as of 13 April 2022 (http://faculty. nelson.wisc.edu/treves/archive_BAS/funding.pdf) and a CV for disclosure of potential competing interests (http://faculty.nelson.wisc.edu/treves/ archive_BAS/Treves_vita_latest.pdf). This does not alter our adherence to PLOS ONE Policies on sharing data and materials Trenches reduce crop foraging by elephants where smallholder farms abut forest parks containing vulnerable species, including elephants (Loxodonta cyclotis and L. africanus) [1]. Though other wildlife such as baboons (Papio spp.) may cause more frequent damage, elephants often have more severe consequences for individual farmers [2–4]. Elephants can destroy entire fields overnight [3], and people lose time, money, and even education or job opportunities if they regularly guard their fields or invest in deterrents [5,6]. Elephants can also be deadly, on occasion seriously injuring or killing people when foraging either in the forest or in adjacent farms. Conflict perpetuates negative perceptions of protected areas and may spur retaliatory killing of wildlife and initiatives to downsize parks [7,8]. African forest elephants (L. cyclotis) are critically endangered and most populations have crashed under hunting pressure and habitat loss [9–11], but savannah elephant (L. africanus) and hybridized African elephant populations are rebounding in some forest parks [12,13]. Rebounding populations confined to parks cannot migrate across their historical range [14], and cause conflict when they cross into agricultural land. Yet to date, at rainforest sites there is limited systematic assessment of elephant crop foraging over time and limited empirical tests of barriers to elephant movement (but see [15], which also highlights how quality of the deterrent or barrier impacts effectiveness). Efforts to reduce crop damage by elephants often include some type of fence, e.g. beehive [15,16], electric [17] or chili (Capsicum) [18]. These barriers are most successful when deployed at the community level because the large scale of elephant foraging renders individual measures ineffective or may only shift the damage to unprotected farms [3,19,20]. Planting large-scale buffers of low-palatability crops, e.g. tea [21] shows promise but this approach is not feasible for smallholders [22,23]. Sustainability and scala (...truncated)