First density and abundance estimate for the only East African Population of Western bongo (Tragelaphus eurycerus eurycerus) in Semuliki National Park, Uganda

In the quiet corners of the world's great forests, large mammals often live lives that are largely invisible to us. For many species, we know very little about how many individuals exist, where they gather, or whether their numbers are growing or shrinking. This lack of information creates a significant gap in our ability to protect them. Conservation planning relies on having a clear picture of a population's size and density, which is simply the number of animals living in a specific area. Without these basic facts, efforts to save a species can feel like guessing in the dark. When a population is small and isolated, such as a group of animals living in a single national park far from their main range, understanding their status becomes urgent. If we cannot count them or understand how they use their home, we cannot effectively shield them from threats like habitat loss or poaching.

This need for clarity drove a team of researchers to the dense woodlands of Semuliki National Park in Uganda. Their target was the Western bongo, a striking forest antelope that is rarely seen and poorly understood across its entire range. While these animals are known to exist in other parts of Africa, the population in Semuliki represents the only known group of Western bongos in all of East Africa. For a long time, the status of this specific group was a mystery. To solve this, the scientists set up a network of cameras throughout the park, capturing thousands of days of footage between late 2019 and mid-2020. They were not just looking for any sign of the animals; they were looking for enough clear images to identify individual bongos by their unique coat patterns, much like recognizing a person by their face. This method allowed them to move beyond simple sightings and build a statistical picture of the herd.

The cameras captured the elusive animals on seventeen separate occasions, revealing a total of eighteen distinct individuals. Among these were eleven females and seven males, including seven young ones that had not yet reached adulthood. The presence of these young animals, along with both sexes, indicated that this was not just a transient group passing through, but an established breeding population making the park its home. By analyzing the patterns of where and when these specific individuals appeared, the researchers were able to calculate how many bongos likely lived in the park, even those the cameras never photographed. They found that the density of the animals varied depending on the type of vegetation and the sex of the animal, with greener, more lush areas appearing to support higher numbers.

The final estimate suggests that the park is home to approximately fifty-six Western bongos. This figure comes with a margin of error, meaning the true number likely falls somewhere between forty-one and seventy-two individuals. In terms of space, this translates to a density of roughly six-tenths of an animal per square kilometer. While this number is small, the discovery itself is significant. It provides the first solid, quantitative baseline for this unique population, confirming that a breeding group exists in East Africa where none was previously known to be. The findings highlight that this population is real and established, but it remains small and vulnerable. The study concludes that to ensure the long-term survival of these bongos, conservationists must now move from guessing to structured, ongoing monitoring to watch over this rare and isolated group.