A large-scale aerial survey in South Sudan has revealed a mass migration of six million antelope, the largest terrestrial mammal movement on Earth, more than twice the size of the annual “great migration” between Tanzania and Kenya, which involves around two million wildebeest, zebras and gazelles.
“The South Sudan migration dwarfs any other migration we know of,” said David Simpson, manager of Boma and Badingiro National Parks for the wildlife NGO African Parks, who oversees the area surrounding the two parks through which the migration takes place. “We estimate that the antelope herd is almost three times the size of the East African migration. The scale of it is truly awe-inspiring.”
Despite decades of civil war and insecurity in South Sudan, the region’s animals have persevered.
In 2007, a Wildlife Conservation Society study suggested the South Sudan migration involved about 1.3 million animals. But African Parks, which manages Boma and Badingiro national parks in southeastern South Sudan on behalf of the government, was able to come up with a more accurate count using improved technology and covering a wider area. It equipped two planes with cameras programmed to take a picture every two seconds. This captured 330,000 images, which a University of Juba graduate used to examine them with wildlife-counting software.
“Seeing animals on this scale is something we never imagined still existed on Earth,” said Mike Fahy, Boma and Badingiro Landscape Coordinator for African Parks. “From the air, it felt like we were seeing what the Earth was like thousands of years ago, when nature and humans still coexisted in balance.”
South Sudan’s President Salva Kiir Mayardit said the survey put his country’s wildlife movement “number one in the world”, adding: “As South Sudan continues to develop, we are committed to transforming the wildlife sector into a sustainable tourism industry.”
From April 28 to May 15, 2023, pilots and observers flew over 122,774 square kilometers (roughly the area of Greece), covering the entire known range of the antelope in the Boma-Badingiro-Jonglei region. They also explored areas that had never been surveyed before. As well as antelope, the researchers also recorded other species, including lions, giraffes, buffalo and elephants.
“The biggest challenge is getting the aerial survey equipment on the aircraft, getting the field of view right, and making the adjustments precise and accurate,” Fay said. “Flying at low altitude with large birds like vultures flying all around the aircraft is extremely dangerous, and flying continuously for four hours every day for weeks on end is stressful.”
Estimates put the total for the four antelope species at just under six million: 5 million red-eared sliders, just under 300,000 Tian gazelles, 350,000 triggerfish gazelles, and 160,000 Bohol reedbucks. Fay said this means that “our data show that this Nile antelope migration is the largest on Earth, far surpassing any other known terrestrial mammal migration on Earth.”
The Great Nile Migration is a year-round movement of animals from the southwest to the northeast through Gambella, Ethiopia and back again, probably driven by the presence of good grazing conditions.
As part of the study, 126 animals from 12 species were collared and their migration distances were measured. Eleven collared long-eared bats, the most abundant antelope in the region, were tracked for approximately 2,000 km (1,250 miles) each. The South Sudanese migration is not the longest land mammal migration on Earth; the Alaskan caribou migration is longer at 3,200 km (2,000 miles). However, it is the same distance as the great migration between Tanzania and Kenya, which includes the famous Mara River crossing. And while the South Sudanese migration is the most abundant large mammal migration, it is far smaller in number than the annual bat migration in Zambia, where 10 million straw-colored flying foxes fly from West Africa to Kasanka National Park every year.
Simpson said the findings were a “game changer for conservation in South Sudan” and could represent “one of the greatest conservation opportunities on the planet”.
Although South Sudan is not considered safe for international tourism, Simpson says such vast wildlife sights mean “the tourism potential is enormous. The world’s largest land mammal migration could put South Sudan on the map as a must-see ecotourism destination, but the migration’s defining value right now is food security for local communities.”
The Boma Badingiro Jonglei region is home to many people, many of whom live off the land. Simpson said the survey not only revealed the extent of the area’s wildlife, but also the threats to migratory animals and the human communities that depend on them. These threats include “road expansion, agriculture, charcoal production and commercialization.” “These activities lead to habitat loss, resource depletion and disruption of migration routes, ultimately threatening the survival of migratory animals and the livelihoods of local people,” he said.
“By ensuring the health of the ecosystems on which migration depends, we can ensure the livelihoods of people throughout migration regions.”
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