TRENCHES What are trenches? These are a type of physical barrier for elephants and other wildlife. These barriers are used for preventing elephant exit outside forest reserve areas or entry into cultivated fields or human habituated areas. They may be used to guide elephants through funneling to over bridges or underpasses.
Case study Around Kibale National Park (Uganda) trenches have been excavated to restrict movement of elephants onto adjacent farmland. Credit: Gross, E. M., Lahkar, B. P., Subedi, N., Nyirenda, V. R., Lichtenfield, L.L., Jakoby, O. (2019) Does traditional and advanced guarding reduce crop losses due to wildlife? A comparative analysis from Africa and Asia, Journal for Nature Conservation, Volume 50, August 2019, 125712.
They require wider environmental consideration, maintenance and management.
Uganda
The trench is excavated two meters deep and two meters wide, and the soil is piled up to form a rampart along the trench.
2 meters
Why do they help?
2 meters
Newly dug and well-maintained trenches have proven reliable in keeping out elephants. According to Gross (2019) Farmers living around Kibale NP regard the trench, which is mainly paid by NP revenues, as very useful. Elephants cannot jump, so a trench that is too wide or deep may act as an effective barrier. These are suitable as permanent installations where soils are stable enough to allow digging and where soil erosion is limited. Trenches can be dug on dry and flat land. They cannot be dug on a slope or in areas prone to flooding as trenches will fill with water, allowing elephants to swim across. Try not to cut down trees, bush or vegetation to create trenches. This will affect the local ecological balance and cause further erosion.
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Bull elephants may still enter the trench and use their trunks to push the mud back into the trench and make it easier for them to climb back out on the other side. Elephants are very intelligent and may habituate or find ways across.
Credit: Gross, E. M. (2019) Tackling routes to coexistence, Human-Elephant conflict in SubSaharan Africa.
PROS
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cons
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Soil erosion - Promotes further erosion, especially during the rainy season. Trench walls need maintenance.
Materials - Can be constructed without too many materials. Manly man power and tools. Cost - Can be a low-medium cost option.
Maintenance - The success of the trench lies in its maintenance, which can be labour intensive and costly,particularly after heavy rains.
Reduction in visits of other crop raiders. Trenches may prevent access from other frequent crop raiders.
Limitations – when soil topography does not support digging trenches (too steep) or where water bodies are cutting through. Physical barrier to people and livestock
Physical barrier to people and livestock.
Dangerous – Elephants or other animals and livestock could be injured or get trapped by falling into deep trenches.
Long term strategy to help restrict elephant entry or exit.
Elephant babies are particularly vulnerable to falling in trenches or getting stuck
What else should they be used with?
Can be dangerous for humans too. Restricted access - Elephants might still find a way to get across – stories of elephants pushing down trees or pushing mud in the trench to find a way across or elephants may move along the trenches to look for crossing points. In case they find crossing points and enter into croplands, chasing them back to parks may become difficult as the access back is blocked. Mixed results and this is not the most effective method.
Use with combined deterrent methods – e.g beehive fencing or chilli fencing.
Considerations Environmental considerations and impacts These are not highly recommended for possible large-scale changes in landscape. Trenches may affect or block natural migration routes for other animals.
DO NOT use spikes or other sharp objects. These are very dangerous to elephants, other wildlife, livestock and people.
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Best to first trial and adapt other methods and farm-based deterrents. Could have long term consequences. These are not recommended on slopes, or areas with water bodies.
Plant trees or vegetation Plant trees, vegetation or a cover crop to stabilize and prevent soil erosion. They are prone to soil erosion, especially along slopes and high rainfall areas.
Combined measures Combine trenches with an electric or beehive fence built on the farm side of the trench for a combined elephant barrier. Ensure one side of the trench is sloped so elephants don’t get stuck and can climb back out.
Maintenance and management
Permissions and research
Due to soil erosion, and especially after heavy rains – trench walls can become weak making it easy for elephants to cross.
Relevant permissions from authorities may be needed.
Must be used in conjunction with other measures and most importantly needs to be well maintained.
Try avoid cutting trees and vegetation.
Long term research needed.
Collaboration with neighbours Work with your neighbours and community to find the most suitable methods for coexistence. Work with local government and wildlife authorities on landscape management.
Caution tips:
Trenches may include large-scale adaptions and a significant change to a localized environment. Use other methods or ideas before resorting to this method. Find out more about the suitability of this method in your environment and what the long-term implications may be. This doesn’t work in all contexts * More site-specific research is needed! Must be used in combination with other deterrents. Trenches may become weak over time due to an accumulation of soil and rubble. Maintenance is required. The consideration and management of elephant migratory corridors is needed.
Large scale trenches require high investment and are difficult to maintain. Pave the trenches with concrete, if resources are available. Best to have a long-term management plan. For best management – creation and maintenance of elephant-proof trenches should be handed over to the district administration or local authorities.
Digging a trench may cause a microenvironmental disturbance, changing dynamics in an ecosystem . It may affect species living in that area, as well as vegetation, water flow and tranquillity.
Note/ Disclaimer This has been used, with mixed effectiveness in Asia.
Success or effectiveness is dependent on various different factors.
Maintaining and protecting wildlife corridors is important for elephant movement.
** Trenches require wider environmental consideration, maintenance and management. Elephant proof trenches should be installed with discretion only where the situation demands.
Only use if completely necessary.
Credits and Disclaimer: The ideas presented here are from various sources and based on case studies. This method has been used with mixed effectiveness. See References. Save the Elephants advises caution with all the methods collected and presented in this toolbox. Further research may be required before each site-specific implementation. *Save the Elephants is not liable for any costs or damages incurred by the use of these methods.
See document on Elephant-aware behaviour
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