In the circle of life, nothing merely disappears — especially not something as massive as an elephant, which can weigh up to seven tons during its 70-year lifespan.
Research published Monday in Proceedings of the National Academy of Sciences details how elephant carcasses shaped the savanna up to almost a decade after their deaths, finding that they triggered bare spots on the landscape before transforming into nutrient-rich hubs of vegetative growth and feeding.
The study was inspired by how frequently researchers passed elephant carcasses while doing fieldwork on the savanna of South Africa’s Kruger National Park, said Courtney Reed, an ecologist at Princeton University and co-author of the new research.
Over the course of two years, Reed and her colleague visited 40 carcasses of elephants that died between eight days and almost eight years prior. At each site, the scientists analyzed levels of nutrients such as ammonium and phosphorus in the soil and the grass. They also measured how well-nibbled the local vegetation was and set up cameras to see who stopped by for a snack.
The results were striking.
“Initially, just everything dies,” Reed said, because the elephant’s fallen body kills off all plants in the area by blocking sunlight.
The study adds to the limited research of how animal carcasses can reshape their surroundings.
“We are really only fairly recently starting to get a handle on how large animals shape their ecosystems altogether, even in life,” said Amanda Subalusky, an ecologist at the University of Florida who was not involved in the study. “We are just beginning to scratch the surface on the role that their carcasses play.”
The latest study found that the devastation of an elephant’s death lasts even after the carcass seems to have disappeared, and it affects microbes as well as vegetation.
“We actually got these biodiversity ‘cold spots,’ where microbial and plant biodiversity were really extremely suppressed,” she said. Reed and her colleagues realized that these bare zones were caused by a flood of such nutrients as nitrogen-rich ammonium. “Too much of a good thing is not actually always good,” she said.
Only certain species were able to gain a foothold amid the extreme conditions.
However, what few species of grass that were able to grow boasted high levels of nutrients themselves, attracting hungry herbivores (that proceeded to produce their own nitrogen-rich waste). Even the oldest carcasses in the study, almost eight years after the animal’s death, showed these elevated nutrient levels and increased grazing.
“We’re still not capturing the full effect, and we don’t know how long it lasts,” Reed said.
But they know it’s much longer than afterlives scientists have seen from smaller animals, which create nutrient pulses that last two or at most five years.
Given that, seeing elephants’ impact continue for eight years with no end in sight was surprising, said Philip Barton, an ecologist at Deakin University in Australia who was not involved in the new research. “There are hidden processes occurring underground all across our landscapes, and they are critical to driving ecosystem structure and function.”
It’s additional evidence that in life and after death, animals gather and move nutrients in ways scientists don’t always notice, Subalusky said. “I think these landscapes really carry the footprints of animals well after they’ve disappeared from the landscape.”
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