T. Rex Smackdowns May Have Ended With Loser Becoming the Meal

Tyrannosaurus rex, one of the largest carnivores ever to live, may have picked fights with his own kind and eaten his slaughtered relatives for lunch, according to a study.

The new insight into T. rex aggression and possible cannibalism comes from an examination of bite marks on four sets of tyrannosaur bones, published online today in the journal PLoS One. The size of the marks suggest they could only have been made by another T. rex, the study researchers said.

It’s not clear whether the T. rex, which went extinct about 65 million years ago, was scavenging already-dead members of its own species or whether the 40-foot-tall dinosaur ate rivals it felled in battle, according to the study published online today. Large predators, such as bears, hyenas, lions and alligators, often feed on their own kind, the authors wrote. In some other predatory species, such as the bald eagle, scavenging is a part of the diet. The tyrannosaurus may be doing both, said Nicholas Longrich, a geologist at Yale University.

“Predators take the path of least resistance, and if there’s something dead, they’ll eat it,” said Longrich, the first author of the study, in a telephone interview. “There’s also a territorial pressure there, and if you want to settle the argument, you might as well settle it permanently.”

In current predators, such as the American alligator, cannibalism occurs because an established adult wants to fend off rivals, and about half the deaths in young alligators are due to cannibalism, Longrich said.

Bite Marks

The marks found on the T.rex bones vary in size, with smaller marks from possible juveniles suggesting scavenging, and larger marks suggesting the end result of fighting. All the marks were definitely made after death, the paper said.

The bones were from fossils found in western North America and dated to the late Maastrichtian period about 65 million years ago. It’s unlikely that the marks could have been made by other large predators because T. rex is the only large meat- eater known from that period and location, the study said.

“I’ve seen other things biting tyrannosaur bones,” Longrich said. “These are too big at that time and place for anything else. There’s no other possibility.”

To contact the reporter on this story: Elizabeth Lopatto in New York at elopatto@bloomberg.net.

To contact the editor responsible for this story: Reg Gale at rgale5@bloomberg.net.