The surprising afterlife of an elephant in the African savannah

Across the sun-baked plains of the African savannah, elephants are bringing new meaning to life after death.

At least, that’s according to the findings of a new study by an international team of researchers who examined the sites of elephant carcasses in South Africa’s Kruger National Park.

These gentle grey giants — often referred to as “ecosystem engineers” — are known to shape the savannah when they’re alive, excavating waterholes, knocking down trees and consuming copious amounts of vegetation. That much, researchers knew already. 

“What we didn’t know was whether those impacts that are so significant when they’re alive could actually continue after they die,” Courtney Reed, lead author of the paper published in Proceedings of the National Academy of Sciences of the United States of America on Monday, told As It Happens. 

“Their bodies contain so many nutrients, tons of carbon and nitrogen and phosphorus, we wanted to understand if the nutrients from those carcasses could actually continue to play a role in the ecosystem.”

By studying soil chemistry, biodiversity and animal grazing around the megacarcasses, the researchers found that decomposition released “enormous pools of nutrients” into the earth. This stimulated soil microbial activity and helped nutrient-rich plants grow, attracting herbivores to the site long after any remaining signs of the elephant carcass.

The effects of decomposition last for more than seven years after the elephants die, the researchers found.

But that burst of regrowth and biological activity doesn’t happen right away. In fact, the caracasses’ high concentration of nutrients initially kills off vegetation on the site, leaving large bare patches or “cold spots” in biodiversity, Reed said.

The study found that the high concentration of nutrients in elephant carcasses initially kills off vegetation around the place of decomposition, leaving large bare patches or ‘cold spots’ in biodiversity. (Submitted by Courtney Reed)

“Too much of a good thing isn’t always a good thing,” she said. “You have this huge pulse of nitrogen, often in the form of ammonium, which at really high concentrations can actually be really toxic to plants.”

Over time, however, Reed says the ecosystem begins to recover as the excess ammonium dissipates and bacteria convert some of it into nitrate, a form of nitrogen that plants can more readily absorb.

Reed says the vegetation that returns is particularly rich in nitrogen, an important source of protein for herbivores.

“Then you have herbivores like zebra and buffalo and rhinos who are all coming in and they’re selectively chewing on these nitrogen rich grasses,” she said. “So you actually get this burst of herbivore activity that continues for years after the elephants died.”

And the benefits don’t stop there. Researchers found that grazing animals continue to visit these burial sites years later, further enriching the soil through their waste.

For Reed, that cycle of renewal is one of the study’s key takeaways: the potential for positive feedback loops to keep influencing the surroundings long after the elephant’s death.

Researchers found that grazing animals and scavengers continue to visit the site of the carcass years later, further enriching the soil through their waste. (Submitted by Courtney Reed)

But the ecological legacy of an elephant carcass isn’t necessarily a positive one in every landscape, suggests one expert unrelated to the study.

Chase LaDue, elephant ecologist and curator of research at the Oklahoma City Zoo, said the paper’s findings highlight how delicately balanced an ecosystem must be. In the African savannah, where biodiversity is shaped in part by natural disturbances, an elephant carcass can help sustain the ecosystem, he said, but if the habitat has shrunk due to humans encroaching on it, those carcasses can instead disrupt the balance.

“If enough elephants die in a very concentrated space, that has an impact on the biodiversity that sort of can’t be spread out as it would in a more undisturbed larger landscape,” LaDue said. “This area of southern Africa has a lot more elephants than the landscape can support and so this just may be another reason even after the elephants have passed, that the landscape is negatively impacted by being so restricted by human activity.”