It may lessen tyrannosaurus rex’s box office cachet as a scary villain, but dinosaur expert Jack Horner said his research pegs T. rex as more like a hyena than a lion.
That is to say, the big fellow was more of a scavenger than a top-of-the-food-chain predator.
“This is the first time I’ve published a scientific paper about it,” Horner said, although he advanced the idea about T. rex’s diet almost 20 years ago. “So it is nice to see that the data support the hypothesis.”
Horner, curator of paleontology for the Museum of the Rockies in Bozeman, collaborated with Mark Goodwin of the University of California at Berkeley on a paper published in the Feb. 9 issue of the journal PLoS ONE, a peer-reviewed scientific and medical publication. The paper was based on specimens collected during 10 summers of excavations in Eastern Montana near the shores of Fort Peck Reservoir, work that began in 1999.
“Our goal was to take a detailed look at the fossil record,” Goodwin said. “Not just the upper level, but look at the entire Hell Creek formation. That’s how you start to see the trends.”
Although Horner’s claim about T. rex may have been greeted with skepticism years ago, he said it’s a fairly widely accepted theory now. The assertion is based on the number of T. rex fossils found compared with those of other dinosaurs of the same period about 65 million to 95 million years ago.
The survey found there were too many T. rex fossils among those of other dinosaurs to believe that T. rex made its living as a predator.
“I knew we would find a lot of triceratops,” Horner said — what Goodwin called the rats of the Cretaceous. “I thought we would find more duckbills. But because of how big tyrannosaurus is, even as a scavenger, I didn’t think there would be so many of them. But that was before I understood the Serengeti.”
The African Serengeti is one of the oldest complete ecosystems in the world, a vast grassy plain where herds of wildebeests and zebras are still hunted by lions and cheetahs, and where packs of hyenas roam as opportunistic feeders.
“If you count the lions and the leopards and the cheetahs in the Serengeti, the number still does not equal the number of hyenas, because hyenas have a much wider food source,” Horner said. “Cheetahs, for example, only go after things that are really fast. They don’t eat turtles. But a hyena will eat a turtle, or anything else that it can catch or is dead.”
By finding adult, subadult and juvenile T. rexes — fossils that others had originally classified as different species — the researchers were also able to see the changes in the dinosaur’s physical makeup, such as how T. rex’s teeth changed in size and number as it aged.
“It could have been exploiting different parts of its prey or some different food than it did as a juvenile,” Goodwin said, with young T. rexes mostly eating flesh, while older ones could use their strong jaws to consume bones and marrow.
T. rex aficionados shouldn’t feel jilted by the researchers’ findings.
“It’s still an impressive member of that age of the dinosaurs, however you look at it,” Goodwin said.
This first paper is just the beginning of mining the wealth of data obtained from the 10 summers of fossil collection.
“This is sort of the overview,” Goodwin said. “But we’ll continue to look at how these animals grow because they are so bizarre. They go through really extreme changes. Why do they do it?”
Also in the works is a book on triceratops. And a closer examination of the plants existing at the time should provide a clearer picture of the climate during the era of the dinosaurs.
“Certainly we’re filling in a lot of the picture, giving a more detailed window into what things were like at the end of the dinosaurs in Montana,” Goodwin said.
Horner said the amount of information his group was able to find was surprising, given that it was in an area where previous groups had collected so many dinosaur fossils before them.
“We didn’t expect to find so much,” he said.
And they didn’t expect to find so many tyrannosauruses.
“It does sound kind of funny to say tyrannosaurus was common, though,” Horner said. “Dinosaurs, they’re just darn peculiar.”