In some regions and many nature reserves in Africa there is a lack of salt. Large herbivores in particular – elephants, giraffes and rhinos – often suffer from a sodium deficiency, as a study shows. The wild animals usually settle where there is enough sodium or sometimes migrate long distances to natural sources of sodium. In their search for salt, they are also increasingly moving into areas inhabited by humans, which could be dangerous for both sides.
To ensure that their metabolism, nerves and muscles function properly, herbivores need sodium regularly. For this reason, farm animals such as sheep and cows have long been given licks made from table salt (sodium chloride) or more complex mineral mixtures, which they can use to cover their sodium needs. Wild animals, on the other hand, rely on getting enough of this essential element from their plant food or from natural mineral sources. But where do they find such salt springs in their habitat?
A team led by Andrew Abraham from Northern Arizona has now investigated where the largest free-living herbivores on earth – elephants, giraffes and rhinos – get their sodium. The biologists and environmental scientists evaluated over 4,200 plant samples and used them to create high-resolution maps of the sodium content of plants in sub-Saharan Africa. They then compared these maps with data on the local population density of the largest herbivorous animals. They also analyzed more than 1,300 fecal samples, as a sodium deficiency in the diet can be detected directly in the manure. The team thus drew conclusions about the actual salt supply of these species.
Sodium deficiency determines settlement areas
The evaluation showed that elephants, giraffes and rhinos have enough access to sodium in some places, but in many places only limited access. Depending on the nature of the soil, sea salt residues, rainfall patterns, climate and plant diversity, there are very different amounts of sodium on the African continent. “In Africa, sodium availability in plants varies 1,000-fold from one region to another,” reports co-author Marcus Clauss from the University of Zurich. “In some areas, wild herbivores simply cannot absorb enough salt from their diet.” Elephants, giraffes and rhinos therefore live primarily where there is enough salt. This tends to be more the case in coastal, flat and low-lying regions of southern Africa, the data shows.
These findings may explain why only a few of these large herbivores live in West Africa and parts of Central Africa. There are numerous plant and animal species there, but only a few megaherbivores such as elephants, giraffes and rhinos. Abraham’s team suspects that the local sodium deficiency is the main reason for this. Other factors could also be overhunting and low soil fertility in West Africa. The largest of the species examined suffered particularly badly from the salt shortage, as the researchers found. In doing so, they confirm previous results that herbivores are at greater risk of sodium deficiency the larger their bodies are.
Dispute over salt
Due to the regional salt shortage, some large animals in Africa develop distinctive wandering and searching behavior: “In Kenya, for example, elephants penetrate caves to reach sodium-rich rock faces, while in the Congo they dig for salt in river beds. Rhinos, wildebeests and zebras often gather at salt pans from the Kalahari Desert to the Maasai Mara,” says Abraham. Some megaherbivores also have conflicts over the coveted raw material: “Gorillas fight over particularly salty foods,” says Abraham.
In the future, herbivorous animals in Africa and elsewhere could increasingly come into conflict with humans. “In human-populated areas, drill holes create artificial sodium hotspots,” explains Clauss. Artificial sources of sodium are also created by road salt, mining and other industrial activities. If the herbivores do not find enough sodium in their habitats and subsequently venture into inhabited areas in search of salt, this could be dangerous for both sides. The researchers warn that this must also be given greater consideration in the future when it comes to nature and animal protection, for example when setting up protected areas.
Sources: Northern Arizona University, University of Zurich; Specialist article: Nature Ecology & Evolution, doi: 10.1038/s41559-025-02917-y