Researchers have released new maps documenting the “Great Nile Migration,” the Earth’s largest-known land mammal migration across South Sudan and Ethiopia.

The maps chart the seasonal movements of two antelope species, the white-eared kob (Kobus kob leucotis) and the tiang (Damaliscus lunatus tiang). Every year, around 5 million white-eared kob and 400,000 tiang migrate across 100,000 square kilometers (38,612 square miles) of South Sudan’s wetlands and Ethiopia’s Gambella National Park.

Grant Hopcraft of the University of Glasgow told Mongabay by email that the mass migration of ungulates has “profound impacts” on how the ecosystems function. For instance, the millions of moving animals change the amount, diversity and regrowth of vegetation through grazing and depositing waste. This in turn affects the diversity of insects and birds that eat those plants. Hopcraft is a scientific advisory board member of the Global Initiative on Ungulate Migration (GIUM) under the Convention on the Conservation of Migratory Species of Wild Animals, which published the maps.

“Migrations used to be a common occurrence globally. Now they only occur in a few relatively undisturbed places around the world. Protecting this migration in South Sudan should be a major priority for conservation,” Hopcraft said.

The mapping used GPS data collected over the past 15 years by contributors including Malik Morjan from the University of Juba in South Sudan, Kassahun Abera at the Ethiopian Wildlife Conservation Authority and African Parks, an NGO that manages a network of protected areas across Africa. The maps also built on aerial surveys and tracking data released by African Parks and South Sudan’s Ministry of Wildlife Conservation and Tourism in 2024.

Melinda Boyers, spatial ecologist for GIUM, told Mongabay their detailed mapping revealed the white-eared kob and the tiang “exhibiting several unique movement patterns in response to seasonal floods and human activity.”

The maps can help protect both antelope species, which face threats such as illegal harvesting, habitat fragmentation and increased human access to their core seasonal ranges, GIUM spatial ecologist Steffen Mumme told Mongabay.

“These issues are exacerbated by oil and gas exploration, which may provide roads and easier entry into critical kob and tiang habitats,” he said. “Energy development may create new barriers to movement and potentially increase illegal killing, significantly disrupting kob migrations and triggering population declines.”

Hopcraft said such explorations can also lead to the loss of connectivity between habitats, in turn affecting ungulate genetic diversity.

“Mapping their migration routes gives more precise information on where to direct conservation efforts, where bottlenecks are and where certain areas are essential to protect the entire migration,” Mumme said.

Additionally, the mapping data can help establish no-go zones and wildlife corridors, Hopcraft said. He added that GIUM plans to distribute large prints of the maps to government partners, educational institutions and schools through an outreach program led by Morjan and supported by the local advocacy group White-eared Kob Heritage Society.

Banner image of tiang in South Sudan ©Marcus Westberg/African Parks.