Why some wildebeest are becoming weaker

Joseph Ogutu, senior researcher and statistician at the University of Hohenheim in Germany, explains why Africa's wildebeest that can't migrate are becoming genetically weaker.

- Joseph Ogutu

"Wildebeest, large African antelopes with distinctively curved horns, are famous for their great migrations on the grasslands of East and Southern Africa. One hundred and fifty years ago they migrated in huge numbers across the continent in search of grazing and water and to find suitable areas for calving.

Migration is crucial to sustain their large populations. But their routes are being interrupted by roads, oil and gas pipelines, railway lines, fences, cities, livestock and farmland.

Today, the only remaining large migration is East Africa's famous Serengeti-Mara migration. About 1,4 million wildebeest, accompanied by about 200 000 zebras, 400 000 gazelles and 12 000 eland, cover up to 3 000km every year in a cycle that follows seasonal rainfall patterns.

Even this migration is now threatened by plans for new roads and railways, uncontrolled and unplanned developments and exponential human population growth around the edges of the Serengeti-Mara ecosystem.

We've now found, in new research, that the disruption to the migratory route has genetic implications for the animals' longer-term survival. Our results show that wildebeest populations that no longer migrate are less genetically healthy than those that continue to migrate.

Because their populations aren't mixing with other wildebeest groups, they are more inbred and genetically isolated. We expect this to lead to lower survival, reduced fertility and other debilitating health effects.