T. rex probably hunted in packs rather than going solo

Utah discovery provides evidence of behavior

Tyrannosaurs probably hunted in packs, scientists announced Monday after analyzing fossils unearthed in Grand Staircase-Escalante National Monument, a conclusion challenging long-held assumptions that the dinosaurs were solitary predators. The new findings could provide fresh support for the Biden administration as it considers expanding the boundaries of a protected area in southern Utah that President Donald Trump cut in half in 2017.

The surprising discovery in the monument’s Rainbows and Unicorns Quarry — so nicknamed because researchers have unearthed a bounty of key finds there — provides fresh evidence that tyrannosaurs were social predators. The research team evaluated physical and chemical elements to determine that four or five Teratophoneus (pronounced Ter-at-oe-fohnee-us) died together during a seasonal flood that washed their carcasses into a lake. The bones, which sat largely undisturbed for a lengthy period, were later shifted as a river churned its way through the area before evaporating.

“A lot of researchers feel like these animals simply didn’t have the brain power to engage in such complex behavior,” paleontologist Alan Titus, who discovered the quarry site in 2014, told reporters in an online briefing. But this discovery, along with other recent findings, suggests otherwise, he said. “This must be reflecting some sort of behavior and not just a freak event happening over and over again.”

The researchers are still exploring why the tyrannosaurs would have hunted together but say a collective effort helped them compete against large, plant-eating dinosaurs.

“This discovery should be the tipping point for reconsidering how these top carnivores behaved and hunted across the Northern Hemisphere during the Cretaceous,” said Joe Sertich, dinosaur curator at the Denver Museum of Nature & Science and one of the project contributors.