ATHENS, Ohio, May 10 (UPI) -- While adult tyrannosaurs used their size and a powerful bite to kill large prey, youngsters used speed and agility to hunt smaller game, U.S. researchers say.
"It's one of the secrets of success for tyrannosaurs -- the different age groups weren't competing with each other for food because their diets shifted as they grew," Ohio University paleontologist Lawrence Witmer said.
Witmer and an international team of scientists from Japan, Mongolia and the United States analyzed the the most-complete known skull of any species of tyrannosaur, providing new clues to the growth and feeding strategies of these ancient predators, an OU release said Monday.
The 70-million-year-old skull is of a very young individual of the Mongolian dinosaur species known as Tarbosaurus bataar, the closest known relative of T-rex.
"We knew that adult Tarbosaurus were a lot like T-rex," Takanobu Tsuihiji, a former Ohio University post-doctoral fellow now at the National Museum of Nature and Science in Tokyo, said. "Adults show features throughout the skull associated with a powerful bite … large muscle attachments, bony buttresses, specialized teeth.
"The juvenile is so young that it doesn't really have any of these features yet, and so it must have been feeding quite differently from its parents."
Adults probably had a life expectancy of about 25 years.
"This little guy may have been only 2 or 3, but it was no toddler … although it does give new meaning to the phrase 'terrible twos,'" Witmer said. "We don't know to what extent its parents were bringing it food, and so it was probably already a pretty capable hunter.
"Its skull wasn't as strong as the adult's, and would have had to have been a more careful hunter, using quickness and agility rather than raw power."