T-Rex 'Gangs' Hunted in Packs

What's worse than one Tyrannosaurus rex? Three. Newly discovered T. Rex tracks show that three of these ancient predators stalked together across a mud flat in ancient Canada supposedly in search of prey, backing the theory that they hunted in packs, according to a new study.

Some 70 million years ago, the ferocious beasts may have "stuck together as a pack to increase their chances of bringing down prey and individually surviving," study co-author Richard McCrea, a curator at the Peace Region Palaeontology Center in Canada, said via Live Science.

The parallel dinosaur tracks relight the debate as to whether T. rex and its cousins, such as Albertosaurus, hunted alone or in groups.

While most researchers believe that they were loners, multiple Albertosaurus specimens found in a single bone bed in Canada's Dry Island Buffalo Jump Provincial Park have led some to propose that tyrannosaurs were pack animals.

Just because a whole group of dinosaurs end up buried together doesn't mean that they necessarily lived and hunted together. Fossils can move or skeletons can accumulate in one location - for instance, the La Brea Tar Pits in Los Angeles, which reopened last month.

In 2011, a local hunting outfitter and guide, Aaron Fredlund, unearthed two tyrannosaur track marks in the foothills of the Canadian Rockies in British Columbia. When McCrea and his team were told about it, they eventually found a patch 197 feet (60 meters) long by 13 feet (4 m) wide filled with fossils of several dinosaur species. They unearthed a total of seven dinosaur tracks, including tyrannosaurs, other small theropods, and duck-billed dinosaurs called hadrosaurs.

The tracks held up for this long because a thick layer of volcanic ash preserved them.

Though the tracks are all going every which way, the tyrannosaur tracks were of particular interest because they were running parallel to each other, suggesting they were traveling together.

"An individual wolf would not be able to take out a moose, but a pack of them would," McCrea said of their possible hunting behavior.

Researchers, however, still cannot determine which species of T. rex created the tracks. Three large tyrannosaurs - Albertosaurus, Gorgosaurus, and Daspletosaurus - all lived in western Canada at the time the tracks were made.

The track marks were described on July 22 in the journal PLOS ONE.