Dinosaurs roamed in multi-species herds, fossilized footprints show

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In Africa, wildebeest and zebra roam the plains in multi-species herds. The blended communities aren’t random animal amalgamations–zoologists believe the populations coalesce for mutual defense against predators. But based on recently discovered footprints in Alberta, Canada, paleontologists now suspect the tactic isn’t a modern evolutionary development—even dinosaurs may have participated in similar multi-species herding patterns. The findings made at the Dinosaur Provincial Park UNESCO World Heritage Site were detailed in a study published in the journal PLOS One.

The environment of present-day Alberta is radically different from its Cretaceous Era past. Instead of windswept fields and rugged, snowy mountains, the region’s lush, subtropical conditions of 76 million years ago provided ample resources for both terrestrial and flying dinosaurs. Species including the Tyrannosaurus rex walked beside eastward flowing rivers that emptied into a warm, inland sea populated by ancient fish, marine reptiles, and sharks.

Tyrannosaurid tracks found at the team's excavation site. — *Tyrannosaurid tracks found at the team’s excavation site. Credit: Brian Pickles / University of Reading*

Since 1979, Dinosaur Provincial Park has provided paleontologists with troves of fossilized remains, mostly in the form of skeletons and bone fragments. But until recently, many researchers didn’t dedicate much time to locating any potential footprints left behind by the various species.

“I’ve collected dinosaur bones in Dinosaur Provincial Park for nearly 20 years, but I’d never given footprints much thought,” University of New England paleontologist Phil Bell said in a statement.

In July 2024, Bell and an international team of colleagues visited the park for a field course. While there, they discovered a set of at least 20 full and partial dinosaur footprints preserved in a roughly 312-square-foot section of sediment. But unlike past finds, the tracks didn’t all belong to one type of dinosaur. Instead, paleontologists eventually matched them to multiple different species. A total of 13 prints were linked to at least five ceratopsian (horned) dinosaurs walking side-by-side, while another grouping likely indicates the presence of an ankylosaurid among them. One footprint also appears to belong to a small, unidentified carnivorous species.

“It was incredibly exciting to be walking in the footsteps of dinosaurs 76 million years after they laid them down,” recalled University of Reading paleontologist and study co-author Brian Pickles.

*This digital elevation model of the site illustrates some of the main footprints discovered by the team. Credit: Brian Pickles / University of Reading*

But it was the discovery of two additional footprint sets perpendicular to the herd that potentially provide the best context to the Cretaceous era snapshot. Not far away, a duo of large tyrannosaurs appear to have been stalking the other dinosaurs. Unfortunately, the team’s excavation work couldn’t yield any evidence of an outcome to the tense moment.

“The tyrannosaur tracks give the sense that they were really eyeing up the herd, which is a pretty chilling thought, but we don’t know for certain whether they actually crossed paths,” Bell explained.

Regardless, the confirmation of mixed species dinosaur herding behavior represents a major moment in paleontology, one that could soon open up new possibilities and research opportunities. The team is already eyeing future locations to examine.

“Using the new search images for these footprints, we have been able to discover several more tracksites within the varied terrain of the Park,” Pickles said. “I am sure [they] will tell us even more about how these fascinating creatures interacted with each other and behaved in their natural environment.”