By Lael Gilbert ’01

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In life, big animals create outsized impacts in the places they live. They eat more, live longer, and move further afield than their more compact counterparts. Really big animals — rhinos, hippos, whales, and elephants — are a special class in this revolving natural account. 

When those animals die, their remains represent a tremendous wealth of natural material with the potential for a long-lasting ecological legacy. And those thousands of pounds of disanimated meat and bone earn a name that reflects that big impact — megacarcass.

Surprisingly, researchers don’t yet know all that much about the specific ecological role megacarcasses play in terrestrial environments. Death ending inside an aquatic system on the other hand, tends to be more researched, says Ryan Helcoski, a graduate student from the S.J. & Jessie E. Quinney College of Natural Resources. 

Abyssal ocean floors — the final resting place for many whales — are often sparse and easier to ecologically map, while rivers move remains — such as massive groups of expired salmon — linearly and are relatively easier to measure. But on land, an open, interactive, and vegetated landscape makes the breakdown of really big bodies like elephants a complex puzzle to track. 

Helcoski and his mentor, Johan du Toit, a longtime USU professor and now  director of science at the Zoological Society of London, are working with a team pursuing some of the first research into terrestrial megacarcass ecology in one of the last places on earth where megaherbivores still roam — Kruger National Park in South Africa. With 7,000 square miles of open veld, dense bush, and scattered baobab trees where elephants have (mostly) free rein, it is an ideal place for researchers to answer a very basic question: What impact does a very large dead animal have on its environment?

The biggest dead animals on land are African bush elephants. Male bush elephants don’t reach full size until around 40 years old and can live up to 70. When an animal like that ceases life, it leaves behind 13,000 pounds of raw ecological potential.

When a coyote, woodchuck, or waterthrush meets its ultimate demise, an inevitable chemistry kicks in. Those animal remains are reabsorbed, one way or another, back into a bigger ecosystem. Carrion becomes food for scavengers, fertilizer for plants, or bounty for insects and fungi. Fur and feathers eventually surrender to sunshine, moisture, and microbes, breaking down into keratin components. The stripped bones decompose and weather over the course of years and crumble into soil, releasing calcium, phosphorus, and other minerals. 

That is all compounded exponentially for a megacarcass, which delivers an enormous pulse of nutrients — an intense and temporary infusion of carbon, nitrogen, and phosphorus — into a hungry system. Those elements are critical for any form of life, and depending on the environment, often in short supply.

In the first hours after death, those resources begin to be dispersed. Scavenging carnivores visit and efficiently remove and consume pieces of the carrion. Then things slow down but remain in morbid motion. Helcoski closely monitors bone field dynamics — how the massive femurs and skulls migrate across a site — as part of this NSF-funded project, and what exactly is driving that movement. He also measures bone nutrient deposition, or how the chemical composition in the bones changes over time. 

“I’m looking at whether a bone that’s 10 to 20 years old releases the same amount of phosphorus into the soil as a brand new bone. We are exploring whether older bones may even have a relatively bigger impact on their environment than new ones,” he says.

He’s also measuring the enriched soil found at megacarcass sites, and observing how it impacts plant growth. This can be tricky since the most nutrient-dense and healthiest plants become a magnet for hungry grazers.

“You can’t just measure the height of a plant to gauge the fertility of the soil because the best-growing plants often become the shortest when they are grazed,” he says.

Helcoski hypothesizes there may be a halo effect in the vegetation around megacarcass sites — radiating rings of enriched soil and strengthened plants that fade further out to a baseline normal.

Living elephants, who tend to be fascinated with their dead comrades, add another really interesting factor to some of these sites. They will frequently visit their recently deceased, sometimes standing silently in a group around the carcass. They leave the site and then return often, for at least a year and a half, to investigate and explore, handling tusks, stroking teeth with their trunk tips — perhaps as a way to identify individuals it’s been hypothesized — and vocalizing. 

Visiting elephants drop piles of dung around each carcass, and the dung includes the seeds of their favored food plants, now deposited on nutrient-enriched soil.

“We are thinking that these areas are somehow basically different,” Helcoski says. “Between the nutrient cycling, scavenger activity and elephant traffic, they are in some way set apart from the surrounding ecosystem. We want to know more about what that means, exactly.”

“It’s a project that is designed for exploration,” du Toit says. “We don’t know what we are going to find exactly, but we want to learn how megacarcasses influence biodiversity.”

The work is fascinating and fundamental, which begs the question why these are the first forays into this research topic. The short answer is that the circle of life is surprisingly hard to quantify.

“If a squirrel is ripped to shreds in a forest, that nitrogen will eventually get back into the soil where plants and microbes will take it up,” Helcoski says. “But it is such a small amount, and spread so widely, there is really no accurate way for us to track where the nutrients are going.”

The breakdown of a megacarcass has many of the same functional processes as the squirrel, but the size makes it much more feasible to observe, map, and measure.

“This work is globally important because all terrestrial ecosystems had megaherbivores — and therefore megacarcasses — before humans changed everything so radically,” du Toit says. “And we need to know what patterns and processes in nature have faded away as megaherbivores have disappeared from almost all of their former ranges.”

And Helcoski hopes this knowledge will benefit more than academics. He sees strong potential for using this basic ecological illustration to help people understand the fundamental principle of nutrient cycling. 

“It’s a notoriously hard thing for people to get the hang of,” says Helcoski, who taught high-school level science for a decade. “You usually get graphs and arrows and you are supposed to    absorb all these different and complicated paths completely in the abstract.”

But death is simple and impactful, he says. He plans to use his research to create educational materials that teach nutrient cycling and focus specifically on big deaths and the fascinating ecological processes they ignite.