Scientists have long wondered how the plant-eating hadrosaurs —who lived alongside predators as fearsome as Tyrannosaurus rex —managed to be so numerous everywhere from North America to Asia.
"They are, hands down, the most common dinosaur around," said University of Alberta paleontologist Scott Persons. "That's baffling. They appear so utterly defenceless.
"They've got no armour. They've got no horns. They're the same size as the tyrannosaurs, but compared to the (T. rex) running speed they appear downright poky. You expect a tyrannosaur to have no problem catching them.
"They appear like sitting ducks — and yet they're thriving. Hadrosaurs must have been doing something really, really right."
Persons laid out his theory Wednesday in a book released by the University of Indiana on new hadrosaur research. He thinks duck-bills evaded their meat-eating enemies in much the same way modern zebras survive lion attacks.
"(Hadrosaurs) can be slow and steady and ultimately win the race — if it's a long race."
Persons specializes in understanding the hind legs and tails of dinosaurs. In an attempt to understand how their muscles attached to their bones, he spent many hours dissecting modern reptiles. He combined that knowledge with computer technology that helps researchers reconstruct ancient bits of anatomy and concluded that the legs of hadrosaurs and tyrannosaurs were built quite differently.
The predators had musculature giving them short, fast and powerful strides — perfect for sudden bursts of blinding speed. Hadrosaurs, however, were hooked up for strides that were longer and slower, but more efficient.
That means they could maintain their top speed for longer than the tyrannosaurs. So if the hadrosaurs got enough of a head start, they could usually outrun their predators.
"In order to successfully catch a duck-billed dinosaur, (Tyrannosaurus) has got to get in close," Persons said.
"There's a narrow striking distance. If it's outside of that, it can run really fast, but then it'll get tired out and the hadrosaur will be able to escape."
It's much the same way herds of modern-day zebras guard themselves against lion attacks, suggested Persons.
"If you imagine yourself as a duck-billed dinosaur, you're a social animal. You're surrounded by members of your own herd, which means there are many, many sets of watchful eyes, watchful ears and watchful noses — and they're all on guard for tyrannosaurs."
Plus, a twelve-metre-long tyrannosaur probably had a harder time sneaking up on its prey through the marshes and coastal forest of 67 million years ago than modern-day lions have slinking through grass toward some zebras.
It's an example of how the study of ancient and modern animals can enrich our understanding of both, said Persons.
"The more we learn about modern-day animals, the better we're able to understand dinosaurs."