Sodium Deficiency Emerges as a Key Regulator of African Megaherbivore Distribution

An international consortium of scientists, featuring experts from Northern Arizona University (NAU) and the City University of New York (CUNY), has pinpointed a crucial, previously underestimated element influencing the habitat ranges and population densities of Africa's largest terrestrial mammals. Their research, which appeared in the journal Nature Ecology & Evolution in December 2025, centers on the availability of sodium, commonly known as table salt, within the continent's vegetation.

Dr. Andrew Abraham, the lead author of the study, highlighted the dramatic variability of sodium concentrations in African flora, noting that fluctuations can span a thousandfold. This extreme scarcity effectively renders the mineral a 'luxury item' for wild herbivores across many regions.

For massive grazing animals such as elephants, rhinoceroses, and giraffes, the physiological requirement for sodium—essential for nerve signaling, muscle contraction, and maintaining proper hydration—increases substantially as their body mass grows. This observation strongly supports the hypothesis that the risk of sodium deficiency is directly proportional to an animal's size, whereas this specific mineral is not as vital for plant life. By meticulously cross-referencing detailed maps showing sodium levels in the plant kingdom with population density data and analyses of animal feces, the researchers were able to precisely map out areas suffering from mineral shortage. The previously puzzling patterns in animal distribution now have a clear scientific explanation rooted in this mineral hunger.

These newly identified patterns offer insight into the specific geophagic behaviors exhibited by megaherbivores. For instance, elephants in Kenya routinely undertake migrations toward specific caves, such as Kitum on the slopes of Mount Elgon, where they use their tusks to chip away at sodium-rich rock and soil. This behavior, alongside consuming salt-laden earth from riverbeds in the Congo forests, represents a direct attempt to counteract the mineral deficit in their primary diet.

Furthermore, instances have been documented where gorillas actively compete for the most saline plants available. Similarly, herds of wildebeest, zebras, and rhinos consistently visit natural salt licks stretching from the Maasai Mara across to the Kalahari. These actions are clearly driven by the need to supplement their sodium intake.

The research team posits that this sodium factor may account for the absence of many megaherbivore species in ecologically rich but sodium-poor regions of West Africa. Professor Chris Doughty, an expert in eco-informatics at NAU, emphasized that sodium scarcity plays a significant role in capping the populations of these giants, likely working in tandem with other pressures such as poaching and generally poor soil fertility.

From a conservation management perspective, these findings carry significant weight. A substantial number of existing protected areas are situated within landscapes inherently low in sodium. This situation could unintentionally exacerbate human-wildlife conflict, as animals desperately seeking necessary minerals might venture closer to human settlements. The scientists are strongly advocating that sodium availability must become a key consideration when designating new reserves and developing population management strategies to ensure the long-term viability of Africa's megaherbivore populations.