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Research started at NAU shows salt availability limits population growth among largest herbivores

A giraffe eating salt.
Andrew Abraham
/
Northern Arizona University
A giraffe eating salt.

A new study that started at Northern Arizona University found the amount of salt in an environment significantly limits population growth for Earth’s largest herbivores.

Just like humans, elephants, rhinos and giraffes need salt in their diet to think, move and reproduce. It's key to hydration and muscle function. The study’s lead author, Andrew Abraham, said research he started in his Ph.D. program at NAU has been expanded in his professional career. In the recent study, researchers mapped sodium availability across all of Sub-Saharan Africa.

“What we found was that particularly in West Africa, there was much lower levels of sodium availability and this is exactly where there’s been this long-standing mystery as to why there have been fewer megaherbivores in this area of the continent," Abraham said. "We suggest that sodium may be a really important role, alongside some previously suggested theories such as over-hunting and soil infertility."

Abraham said sodium availability varies over a thousandfold in plants across the continent, meaning in many areas, wild herbivores can’t get enough salt in their diet.

“This confirms previous research that we've done, which has suggested that larger bodied animals may be more vulnerable to sodium deficits," Abraham said. "What we were actually able to find in this study is that it really does make a difference in the density and distribution of these megaherbivores.”

Abraham said climate change also plays a role.

"Salt coming from the ocean is one of the key drivers of patterns of salt variability for wildlife," Abraham said. "Climate change is altering wind patterns, which is influencing where the salt gets deposited and in what quantities. So there is definitely an important role that humans are playing."

At the same time, he said many protected areas are located in low-sodium environments, and humans have created artificial sodium hotspots through various activities like borehole pumping and road salting. He said it raises a number of conservation concerns and if animals can’t get enough sodium in their natural habitats, they may come into conflict with people on their quest to find it.

More Arizona animal news

Senior field correspondent Bridget Dowd has a bachelor’s degree from Arizona State University’s Walter Cronkite School of Journalism and Mass Communication.