Dinosaur footprints are first evidence of mixed species herding

For some dinosaurs, safety was found in numbers.

Footprints uncovered in the Canadian province of Alberta could be evidence that some dinosaurs moved in herds comprising multiple different species.

Many of the newly described footprints were made by ceratopsians, the group of horned dinosaurs that includes Triceratops. The 13 ceratopsian tracks are thought to belong to at least five individuals walking together across the landscape during the Cretaceous Period 70 million of years ago.

But another set of footprints walking among the herd is thought to belong to an ankylosaurid. These are a different group of dinosaurs which includes the tank-like armoured animal Ankylosaurus.

Additionally, two large Tyrannosaurus rex trackways were also discovered walking side-by-side and perpendicular to the herd, which has also raised questions about whether these huge predators were stalking the group.

The discovery was made in July 2024 at the world-famous fossil site Dinosaur Provincial Park. An international team, including scientists from the University of Reading and the Royal Tyrrell Museum of Palaeontology in Canada, was involved in the study, which has now been published in the journal PLOS ONE.

Dr Brian Pickles, a researcher at the University of Reading and an author of the study, says, “It was incredibly exciting to be walking in the footsteps of dinosaurs 76 million years after they laid them down.”

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

What can we learn from these footprints?

Preserved footprints can provide a rare insight into the lives of dinosaurs that we can’t always discern just by examining their bones.

Jack Lovegrove, a palaeontologist at the Natural History Museum, says, “Dinosaur trackways are important as they give us a direct window into dinosaur behaviour. This can help confirm that they displayed behaviour scientists have previously inferred from their bones.”

“Ceratopsians have long been suspected to have lived in herds due to the existence of bone beds which preserve multiple individuals of the same species together. However, these bone beds only tell us for certain that these animals died together or the bodies accumulated after death.”

“The preserved trackways of several ceratopsians walking together in a group is rare evidence for these animals living together.”

The presence of other dinosaur footprints among the ceratopsians has led researchers to believe that these trackways could show the first evidence of mixed-species herding behaviour in dinosaurs. This would have been similar to how modern wildebeest and zebras travel together across the African plains.

The presence of two T. rex footprints also raises the prospect that multispecies herding may have been a defence strategy against common apex predators. Although the research team admits that more evidence is needed to confirm this.

“While it’s tempting to imagine these tracks as representing a single event where two tyrannosaurs are stalking the mixed herd of herbivores, this may not be entirely accurate,” says Jack.

“We don’t know how long the mud flat that preserved these trackways was exposed, so they could have been made days or even weeks apart. We may be seeing a montage of Cretaceous life rather than a single scene.”

A treasure trove of dinosaur discoveries

While dinosaur tracksites have been found in multiple places across the world, this new one is the first of its kind to be discovered in Dinosaur Provincial Park.

Dinosaur Provincial Park is a UNESCO World Heritage site and is home to some of the world’s most important dinosaur discoveries. So far, the remains of at least 44 species across 10 dinosaur families have been identified from the site.

The area is located in the heart of Alberta’s Badlands, but during the Cretaceous Period this area was a coastal plain crisscrossed by rivers and covered in a lush forest.

The site has provided palaeontologists with a large number of high-quality specimens, which have helped us gain a deeper understanding of dinosaurs during this period of time. More than 150 nearly complete skeletons have been made up of material from this site and are now housed in 30 major museums.

Several specimens from Dinosaur Provincial Park are currently housed in the Natural History Museum in London. In 2011, scientists described a new species of medium-sized ceratopsian dinosaur based on material recovered from the site in Canada in 1916. The remains of the species, called Spinops sternbergorum, had been in the collections for almost 100 years before scientists realised its significance.

Today, work to unearth more dinosaur discoveries continues at the site.

“What’s exciting about these trackways in particular is they have been found in the dinosaur park formation, which has one of the best-known dinosaur faunas in the world,” says Jack.

“Palaeontologists have a good understanding of which dinosaurs lived at different levels within this formation and therefore which dinosaurs were the trackmakers at this site.”