Scientists discovered that the amount of salt in plants across Africa varies dramatically—by more than 1,000 times in some places. This variation helps explain why huge animals like elephants and giraffes are common in some African regions but nearly absent in others. Researchers used computer models and field data to map where salt is available in plants, and found that areas with very little salt have far fewer megaherbivores. This finding is important because it shows that salt in the soil and plants is just as important as food availability for supporting large animal populations, and it helps us understand how human activities that change salt levels in nature could affect wildlife.

The Quick Take

  • What they studied: Whether the amount of salt available in plants across Africa affects how many large animals like elephants, rhinos, and buffalo can live in different areas
  • Who participated: Researchers analyzed data from across sub-Saharan Africa, including field measurements of plant salt content, animal droppings to measure salt intake, and population counts of large herbivores
  • Key finding: Plant salt availability varies over 1,000-fold across Africa, and areas with very low salt have significantly fewer megaherbivores. When scientists added salt availability to their prediction models, they could much better predict where large animals would be found
  • What it means for you: This research suggests that salt availability in nature is a hidden factor controlling where wild megaherbivores can survive. Understanding this helps conservation efforts and shows why human changes to natural salt levels could harm wildlife populations

The Research Details

Researchers combined multiple types of information to understand salt’s role in Africa’s large animal populations. They created detailed maps showing where salt is available in plants across sub-Saharan Africa using machine-learning computer models—a technique that finds patterns in large amounts of data. These maps were based on field measurements of actual plant salt content, information about rainfall and soil chemistry, and how different plants absorb salt from their environment.

To verify their maps were accurate, scientists collected animal droppings from wild herbivores and measured the salt content. They found that animals in areas with more plant salt had higher salt levels in their droppings, confirming that the computer maps correctly predicted where animals could get salt from their food.

Finally, they used these salt maps along with other environmental data to predict where large animals should be found. They tested whether adding salt availability information improved their predictions compared to models that only looked at food availability and other factors.

This research approach is important because it reveals a ‘hidden’ factor that controls where megaherbivores can live. Previous studies focused mainly on food availability, water, and predators, but largely ignored salt—even though animals need it just as much as plants need water. By using computer models to map salt across an entire continent and then testing predictions against real animal populations, the researchers proved that salt is a major limiting factor, not just a minor detail

This study is published in Nature Ecology & Evolution, a highly respected scientific journal. The researchers used multiple independent lines of evidence (plant measurements, animal droppings, population data) that all pointed to the same conclusion, which strengthens confidence in the findings. The use of machine-learning models allowed them to make predictions across vast areas where field data wasn’t available. However, the study doesn’t specify exact sample sizes for all measurements, and some regions may have more data than others

What the Results Show

The most striking finding is that plant salt content varies by more than 1,000-fold across sub-Saharan Africa. This enormous variation comes from several sources: salt carried by ocean winds and rain near coasts, how water moves through soil, the chemical makeup of rocks and soil, and differences in how much salt various plants absorb and store.

When researchers measured salt in animal droppings, they found a clear pattern: animals living in areas with more salt in plants had more salt in their bodies. This proved that the computer maps accurately predicted where animals could get salt from their food.

Most importantly, when the researchers added plant-salt information to their computer models predicting where large animals live, the predictions became much more accurate—especially for the biggest animals like elephants and rhinos. Areas with very low plant salt had dramatically fewer megaherbivores, even when food and water were available. This shows that salt availability, not just food, determines how many giant animals can survive in a region.

The research revealed that megaherbivores (the largest animals) are more affected by salt shortages than smaller herbivores. This makes sense because bigger animals need more salt overall, even though they also need more food. The study also identified specific regions in Central and West Africa where salt is extremely scarce, which explains why these areas have very few large animals compared to East and Southern Africa where salt is more abundant

Earlier research suggested that larger animals might be more sensitive to salt shortages, but no one had proven this at a continental scale or shown that salt actually limits animal populations in the wild. This study is the first to demonstrate that salt availability is a major factor controlling megaherbivore distribution across Africa, putting it on equal footing with food and water as a critical resource

The study doesn’t provide exact numbers for how many animals were counted or how many plant samples were collected in each region. Some areas of Africa likely have more detailed data than others, which could affect accuracy in those regions. The research focuses on Africa, so it’s unclear whether these findings apply to other continents. Additionally, the study shows that salt affects where animals live now, but doesn’t fully explain all the historical reasons why some regions lost their megaherbivores

The Bottom Line

Conservation efforts in Africa should consider salt availability when planning wildlife protection areas and reintroduction programs. Areas with naturally low salt may need supplementation if megaherbivore populations are desired. Moderate confidence: This recommendation is based on clear evidence that salt limits animal populations, though implementation strategies need further research.

Wildlife managers and conservation organizations working in Africa should pay attention to this research. Governments planning land use and mining operations should consider how their activities might change salt availability. The general public should understand this as an example of how ‘invisible’ factors in nature control where animals can live. This research is less directly relevant to people in developed countries, though it may inform global conservation strategies

Changes in salt availability would affect animal populations gradually over years to decades, not immediately. If salt is added to an area, megaherbivores might return over several years as populations grow. If salt is removed or reduced, animal populations would decline over similar timeframes

Want to Apply This Research?

  • Users interested in wildlife conservation could track megaherbivore sightings or population estimates in their region and correlate them with seasonal salt availability data (if available locally), noting patterns in animal distribution relative to salt-rich areas
  • For conservation-focused users: Research local salt levels in your region’s soil and water, and advocate for protecting salt-rich habitats. For general users: Learn about your local ecosystem’s mineral composition and how it supports wildlife, then support conservation efforts that protect these natural resources
  • Long-term tracking could involve monitoring megaherbivore population trends in your region over years, documenting changes in salt availability through soil testing or water analysis, and noting correlations between salt levels and animal abundance. Users could participate in citizen science projects that track wildlife populations in relation to environmental factors

This research describes patterns in wild animal populations and salt availability in Africa. It does not provide medical advice for humans. While sodium is essential for human health, individual dietary needs should be discussed with a healthcare provider. This study’s findings about wildlife should not be used to make decisions about human salt consumption or supplementation. Anyone considering changes to their diet should consult with a doctor or registered dietitian.