A new study reveals that one‑horned rhinos, 12 million years ago, weren’t solitary wanderers but members of vast herds that congregated around watering holes in what is now Nebraska.
Published in Scientific Reports, the research harnesses isotopic “fingerprints” from fossilized rhino teeth to track their movements — and the results challenge previous ideas that these Miocene beasts migrated long distances or only gathered in response to disasters.
“We found they didn’t move very much,” lead author Clark Ward said in a statement, “We didn’t find evidence for seasonal migration or any evidence of a response to the disaster.”
Ward and his colleagues analyzed strontium, oxygen and carbon isotopes in the enamel of Teleoceras major teeth excavated at Ashfall Fossil Beds State Historical Park, where more than 100 rhinos were buried under ash from a mid‑Miocene Yellowstone supereruption. Strontium ratios reveal the geographic origin of the animals’ diets, oxygen tracks local water sources and climate, and carbon hints at the vegetation they consumed—together painting a picture of sedentary, water‑bound herds rather than nomadic graziers.
Incorporating key insights from a complementary isotope study, the team also serially sampled molar enamel to examine short‑term shifts in diet and mobility. This approach confirmed that all individuals remained “local to Ashfall” throughout tooth formation, indicating a herding behavior sustained year‑round rather than seasonal migration or emergency gatherings prompted by ashfall.
Teleoceras major, a barrel‑bodied rhino with stubby legs much like a modern hippo, likely spent much of its time in and around water, feeding on C3 grasses and other leafy vegetation. Their massive size would have deterred predators, though hyena‑like bone‑crushing dogs did scavenge the carcasses, as evidenced by bite marks on some fossils.
“By studying carbon in the animal, we can reconstruct carbon in the environment to understand what kinds of vegetation lived there,” Ward said.
Rhino specialist John Payne, who was not involved in the study, praised the findings, “I am not surprised that the analyses very strongly suggest that Teleoceras major lived in herds given that this animal resembles modern hippopotamus in form and hippos live in herds of several tens of animals — with several herds in one geographical area.” He added, “One can readily imagine several herds of many tens of individuals in each herd living in adjacent grasslands.”
Ash from the Yellowstone eruption blanketed western North America and fell like snow across the Great Plains. Unlike the instantaneous burial of Pompeii, the rhinos likely inhaled ash over weeks, starving as vegetation, water and air grew increasingly ash‑laden.
“That ash would have covered everything: the grass, leaves and water,” Ward said. “The rhinos likely weren’t killed immediately … Instead, it was much slower. They were breathing in the ash. And they likely starved to death.”
For Ward—who grew up near Ashfall and once guided visitors through the fossil beds—this research brings his childhood wonder full circle: “I’m honored and privileged to have my name in science attached to the site,” he said.
The study not only reshapes our understanding of Miocene rhino sociality, but it also demonstrates how multi‑isotope analyses can reveal the hidden lives of extinct creatures.
The study has been published in Scientific Reports.
