An ancient predator responded to a climate crisis by shifting from meat to bones.
As heat and scarcity reshaped its world, it evolved new survival strategies—offering clues for animals facing today’s climate change.
Meat-Eater’s Surprising Climate Response
Around 56 million years ago, during a time when global temperatures spiked dramatically, a meat-eating mammal responded in an unexpected way: it began consuming more bones.
That’s what researchers at Rutgers University discovered after analyzing fossilized teeth from the now-extinct predator Dissacus praenuntius. Their study sheds light on how some animals adapted during the Paleocene–Eocene Thermal Maximum (PETM), a period marked by intense climate change. Published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology, the research offers clues that may help scientists understand how modern wildlife could react to today’s warming climate.
“What happened during the PETM very much mirrors what’s happening today and what will happen in the future,” said Andrew Schwartz, a doctoral student in the Department of Anthropology at the School of Arts and Sciences, who led the research. “We’re seeing the same patterns. Carbon dioxide levels are rising, temperatures are higher and ecosystems are being disrupted.”
Associate Professor Robert Scott of the Department of Anthropology is a co-author of the study.
Clues in the Teeth: A Window Into the Past
To uncover the dietary habits of Dissacus, Schwartz, Scott, and a colleague used a method called dental microwear texture analysis. This technique examines the tiny pits and scratches left on tooth surfaces, which reveal what the animal was eating shortly before its death.
Roughly the size of a jackal or coyote, Dissacus was an omnivore that likely fed on meat, fruits, and insects. “They looked superficially like wolves with oversized heads,” Schwartz said, describing them as “super weird mammals.” “Their teeth were kind of like hyenas. But they had little tiny hooves on each of their toes.”
Before temperatures began to rise, Dissacus had a diet similar to that of modern cheetahs, focused mainly on eating meat. But as the climate warmed, evidence from its teeth showed it began crunching harder materials, including bones.
From Cheetah-Like to Bone-Cruncher
“We found that their dental microwear looked more like that of lions and hyenas,” Schwartz said. “That suggests they were eating more brittle food, which were probably bones, because their usual prey was smaller or less available.”
This dietary shift happened alongside a modest reduction in body size, likely because of food scarcity. While earlier hypotheses blamed shrinking animals on hotter temperatures alone, this latest research suggests that limited food played a bigger role, Schwartz said.
This period of rapid global warming lasted about 200,000 years, but the changes it triggered were fast and dramatic. Schwartz said studies of the past, like his, can offer practical lessons for today and what comes next.
Looking Back to Look Ahead
“One of the best ways to know what’s going to happen in the future is to look back at the past,” he said. “How did animals change? How did ecosystems respond?”
The findings also highlight the importance of dietary flexibility, he said. Animals that can eat a variety of foods are more likely to survive environmental stress.
“In the short term, it’s great to be the best at what you do,” Schwartz said. “But in the long term, it’s risky. Generalists, meaning animals that are good at a lot of things, are more likely to survive when the environment changes.”
Survivors and Strugglers in a Shifting World
Such an insight may be helpful for modern conservation biologists, allowing them to identify which species today may be most vulnerable, he said. Animals with narrow diets, such as pandas, may struggle as their habitats shrink. But adaptable species, including jackals or raccoons, might fare better.
“We already see this happening,” Schwartz said. “In my earlier research, jackals in Africa started eating more bones and insects over time, probably because of habitat loss and climate stress.”
The study also showed that rapid climate warming as seen during the ancient past can lead to major changes in ecosystems, including shifts in available prey and changes in predator behavior. This may suggest that modern climate change could similarly disrupt food webs and force animals to adapt, or risk extinction, he said.
Extinction Despite Adaptability
Even though Dissacus was a successful and adaptable animal that lived for about 15 million years, it eventually went extinct. Scientists think this happened because of changes in the environment and competition from other animals, Schwartz said.
Schwartz conducted his research using a combination of fieldwork and lab analysis, focusing on fossil specimens from the Bighorn Basin in Wyoming, a site with a rich and continuous fossil record spanning millions of years. Schwartz chose the location because it preserves a detailed sequence of environmental and ecological changes during the ancient period of climate warming.
Schwartz has been interested in paleontology, specifically dinosaurs, since he was a boy, journeying with his father, an amateur fossil hunter, on treks through New Jersey’s rivers and streams. Now, as a late-stage doctoral student, he hopes to use ancient fossils to answer urgent questions about the future.
Inspiring Future Paleontologists
He also wants to inspire the next generation of researchers.
“I love sharing this work,” he said. “If I see a kid in a museum looking at a dinosaur, I say, ‘Hey, I’m a paleontologist. You can do this, too.’”
Reference: “Dietary change across the Paleocene-Eocene Thermal Maximum in the mesonychid Dissacus praenuntius” by Andrew Schwartz, Larisa R.G. DeSantis and Rob S. Scott, 13 June 2025, Palaeogeography, Palaeoclimatology, Palaeoecology.
DOI: 10.1016/j.palaeo.2025.113089
In addition to Schwartz and Scott, Larisa DeSantis of Vanderbilt University is an author of the study.
Never miss a breakthrough: Join the SciTechDaily newsletter.
Follow us on Google and Google News.