Measuring wildlife degradation, made simple

Camera trap image of a mandrill. Photo by SWM Programme

Medium and large-sized mammals – think duikers (forest antelopes), porcupines, and wild pigs – play critical roles in African tropical ecosystems, such as dispersing seeds, grazing on vegetation, and predating on other animals.

Yet these species are also prime targets for hunters.

When they’re overexploited, these ecosystems start to change, with larger animals disappearing and smaller species like rodents becoming more dominant.

Several indicators have been proposed to assess these changes, but only a few studies have been dedicated to testing them, so their reliability remains uncertain. Now, a just-published paper is moving the conversation forward by providing concrete evidence—perhaps for the first time—on the shifts in species composition and resilience to hunting pressures.

The work in the field was undertaken by a team of researchers in Gabon, West Africa as part of the Sustainable Wildlife Management (SWM) Programme, who tracked these shifts using systematic camera trapping and hunter offtake records. An unprecedented number of hunters—314 from 10 communities—recorded animals and areas hunted from nearly 13,000 hunting trips.

By comparing the wildlife composition in hunted areas with that in protected reference sites, the team developed a collection of indicators that can be used to assess the condition of the hunted wildlife. “The work undertaken by the team in the published paper confirms that simple indicators used by hunting communities can be powerful tools for monitoring wildlife degradation in their hunting sites,” said Hani El Bizri, who put together the list of hunting indicators together with Mattia Bessone for the WILDMEAT Use Database. “By using these indicators, and the knowledge and involvement of local hunters and community members, self-monitoring can be greatly strengthened.”

In the published paper, two key indicators emerged as particularly noteworthy. The first is the rodents-to-ungulates ratio, which increases significantly in heavily hunted areas, reflecting a higher presence of smaller species. The second is the mean body mass of the offtake (the animals that are killed on hunting trips), which decreases as hunting pressure intensifies, indicating a decline in larger species.

“These findings have been suggested from indirect data such as literature reviews,” said co-author Julia Fa, Professor of Biodiversity and Human Development at Manchester Metropolitan University and Senior Research Associate at the Center for International Forestry Research and World Agroforestry (CIFOR-ICRAF), “but our study is the first to use empirical data to demonstrate that the decline in larger, more vulnerable species leads to an increase in smaller, more resilient ones.”

The indicators are both easy to calculate and practical for implementation through community-led monitoring programmes. “By focusing on easily observable and measurable parameters, the toolkit facilitates ongoing wildlife monitoring with minimal resource requirements, making it accessible and sustainable for local communities,” said Fa.

The findings underscore the importance of involving local communities in wildlife monitoring and management. “By empowering local stakeholders with the ability to track wildlife populations and health, the toolkit fosters a sense of ownership and responsibility among community members, promoting conservation practices that are effective and culturally relevant,” said Fa. “The approach recognizes the indispensable role of local knowledge and participation in achieving long-term conservation success, especially in tropical regions where biodiversity is rich and vulnerable.”

Camera trap image of an elephant. Photo by SWM Programme

A key element of the process was ensuring the reliability and accuracy of the data collected from hunter declarations. “Hunters’ knowledge and observations are invaluable, yet there is an inherent challenge in standardizing and verifying such data across different individuals and communities,” said Fa. “Building trust and establishing effective communication channels with local hunters were crucial steps in overcoming this hurdle — highlighting the importance of community engagement and mutual respect in conservation projects.”

The researchers advocate for scaling up this approach across other tropical regions, adapting the indicators to different ecological contexts. They also call for the integration of these methods into broader conservation strategies, including the establishment of community-use zones and the protection of large-scale ecological connectivity.

“By leveraging the expertise of local communities and using these straightforward indicators, we can make significant strides in conserving wildlife and maintaining ecological balance in tropical forests,” said the study’s first author Davy Fonteyn, who led the research in his postdoctoral position at the French Agricultural Research Centre for International Development (CIRAD) within the Sustainable Wildlife Management (SWM) Programme.

“The research process highlighted the value of adaptive and inclusive approaches,” said Fa, “demonstrating that effective conservation requires not only scientific expertise but also the active participation and empowerment of the people who live in and rely on these ecosystems.”