"Mighty" T. Rex Mostly Picked Off Youngsters?

Matt Kaplan
for National Geographic News
August 11, 2009
A mighty hunter has fallen—at least in the eyes of countless kids who admire the fearsome Tyrannosaurus rex.

Contrary to depictions in films, in books, and with plastic toys on the living room rug, T. rex and its large predatory kin very rarely attacked full-grown adult dinosaurs, a new study says.

Instead the famed carnivore was most likely a dinosaur bully, picking off defenseless youngsters.

"Several aspects of the supposed lifestyle of these animals didn't fit with what we knew about the behavior of modern predators," noted study co-author David Hone of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China.

"The titanic fights often depicted were in conflict with the normal style of predation in large predatory mammals, such as lions and tigers, which usually go for the weak and inexperienced."

No Bones About It

The proof lies in markings found on fossil bones from prey animals, according to Hone and co-author Oliver Rauhut, of Ludwig Maximilians Universität in Munich, Germany.

The pair analyzed previous studies of dinosaur bones found around the world.

The fossils belonged to species that lived during the Jurassic and Cretaceous periods, which together span 199 to 65 million years ago.

Predators that had died with meals preserved in their stomachs usually contained just a handful of their prey's bones, Hone and Rauhut report in their paper, which was published online August 3 in the journal Lethaia.

(Related: "'Cannibal' Dinosaur Wrongly Accused, Study Says.")

The prey bones that were found came from young dinosaurs and rarely showed any bite marks. That's because juvenile bones were most likely swallowed whole, since they were softer than adult bones and more easily dissolved in stomach acids.

The researchers then looked at studies of adult bones not found in the guts of fossil predators but known to be prey species.

Those fossils also rarely had bite marks, which would be signs that predators had used their teeth to scrape away meat or gnaw at the bones.

In some cases, injuries that had been inflicted by carnivores showed signs that the wounds had healed, suggesting that the adult dinosaur had been attacked but not killed.

Hone and Rauhut therefore think that T. Rex and its meat-eating kin hunted like modern predators, which selectively attack vulnerable and inexperienced juveniles.

If youngsters were indeed at the top of the predatory menu, that might explain why so few juvenile dinosaur bones have been found so far, the researchers added.

T. rex vs. Triceratops

Thomas Holtz, a paleontologist at the University of Maryland, agrees that predatory dinosaurs' feeding behaviors have been long overdue for a critical eye.

"There hadn't been much quantitative thinking about the battles between T. rex vs. Triceratops," said Holtz, who was not involved in the new study.

"We've all always been intrigued by the [T. rex's] large size, but [this research] is reeling us in and orienting us toward their day-to-day feeding rather than the extreme hunting featured on the Discovery Channel," he said.

"Sure, those big battles did happen, but this work suggests not very often."

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