Posted on behalf of Katrina Charles, BA Media Fellow

Want to improve your species’ chances of survival? Grow fast and large, and start breeding younger.

For the soft-bodied, duck-billed hadrosaur, Hypacrosaurus, this seems to have been the survival strategy. It was one of three common prey for Tyrannosaurus rex and its relatives, but the other two had the advantages of “horns or stout, tank-like bodies” (press release).

Researchers have now found, by looking at thin sections of the long leg bones of a specimen of Hypacrosaurus and counted and measured the growth rings, that these dinosaurs grew much more rapidly than their predators (research paper).

The Hypacrosaurus grew to 9 metres in 10 to 12 years [yahoo]. Tyrannosaurs, however, reached adulthood after 20 to 30 years, said Drew Lee of Ohio University’s College of Osteopathic Medicine [press release]. The adult sizes of the predators ranged from 12 meters in length for Tyrannosaurus rex [livescience] to 1.8 metres for the Velociraptor-like Troodon (LiveScience).

“Our duck-billed dinosaur grew three to five times faster than any potential predators that lived alongside it,” Lee said. “By the time the duck-billed dinosaur was fully grown, the tyrannosaurs were only half grown – it was a huge size difference.”

There is also evidence that this survival strategy is still used (PNAS paper).

Lisa Cooper, of Kent State University in Ohio, said: “We were shocked at how fast they grew. If you look at a cross section of the bone of a nestling or even from within the egg, there are huge spaces in which blood supply was going through the bone, which means they were growing like crazy.”

They also found that the Hypacrosaurus reached sexual maturity in just two to three years. “That’s another added bonus when facing predators — if you can keep reproducing, you’re set, it’s the stuff of evolution,” said Cooper.

One creature not employing this quick reproduction strategy is Henry the tuatara, one of the last living remnants of the dinosaurs, a lizard who is going to become a father at the age of 111 years old (BBC, AP).

Henry has been in captivity since 1970, and these 11 eggs are from the first time he has bred in that time. He had shown no interest in sex until recently when he had a cancerous growth removed from his genitals. He first met the mother, Mildred, a sprightly 80 years old, 25 years ago when he bit off her tail (TVNZ).

Image: Drew Lee/Ohio University