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Trialling AudioMoth to detect the hidden threats under the canopies of Belize

Belize lies on the Mesoamerican Biological Corridor in Central America and is globally renowned for its abundance of biodiversity, with 60% of the land area of the country still covered by forest. The terrestrial ecosystems in Belize are vulnerable to human overexploitation, and disturbances under the canopy can proceed unnoticed, as the rugged terrain makes it challenging to patrol and monitor. For example, poaching, selective logging and the looting of ancient Mayan artefacts are not uncommon occurrences even in protected nature reserves. During May of this year, the Open Acoustic Devices team travelled to central Belize to gain insight into the challenges that organisations face in managing protected areas while also collecting acoustic data that will be used to support the development of reliable anthropogenic disturbance algorithms. These will then be used on our devices to monitor poaching and logging activity.

An old anti poaching poster that was located at the edge of the forest boundary to deter human activity within this area.

Sufficient and timely information on poaching and logging activities is required to manage protected areas and we believe that open acoustic devices will help. A great way to quantify human disturbances is by detecting the sound certain activities make. AudioMoth is our first open-source acoustic device which can be programmed for multiple applications. One of our main goals in its development was to look at a solution to monitor cryptic forest disturbances to support the management of forested areas. The development of the on-board intelligence relies heavily on training data gathered from the field, which in this case is essential for the design of a reliable anthropogenic disturbance algorithm to detect poaching and logging activity. On this field trip we focused on gunshot detection around Pook's Hill and Tapir Mountain Nature Reserve area in the Cayo District. We hiked the surrounding forest deploying over sixty AudioMoths that were set up to capture controlled experimental gunshots.

It was clear, even from our first walk into the forest, that poaching still took place in the area with evidence of shotgun shells and a poacher’s camp, despite anti poaching posters.

A poacher’s camp that we stumbled upon while during this deployment, where we also found empty shotgun shells close by.

Over two weeks we tested the sensitivity of our prototype gunshot detection algorithm and the range of the microphones in the dense rainforest environment. These tests were carried out by deploying devices at regular intervals along a 1.2 km transact and firing two types of shotgun, commonly used for hunting, at set locations. We then gathered a dataset of recordings at various distances and positions.

Factors such as background noise, foliage thickness and topography all affected the way in which the sound of a gunshot propagated through the forest. Actually visiting the site and witnessing the effects of these factors was invaluable for the continuing development of AudioMoth.

While work on the development of the devices and algorithms have recommenced on the return to Southampton, a small grid of devices was deployed around the Pook's Hill and Tapir Mountain Nature Reserve area. Along side detecting hunting activity in the area this grid will help us identify improvements to the design for long-term monitoring. The high humidity and tropical temperatures of more than 30°C in Belize is an extremely hostile environment for electronic devices. It will be interesting to see how the grid has faired in a few months time when we will return to Belize to collect the data from our deployed devices. Hopefully, this will give us an initial insight into the gunshot occurrences around the area and bring us one step closer to identifying the hidden human impact under the canopies of Belize.

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