Scavenger T.rex much more like a hyena than a lion
An epic Montana fossil bed census suggests Tyrannosaurus rex was more of an opportunistic scavenger like a hyena, than an apex predator like a lion. This is the largest study of its kind in the world and the first complete picture of an ancient ecosystem dominated by dinosaurs.
Tyrannosaurus skeletons in Hell Creek rocks are as common as Edmontosaurus, a herbivore, akin to there being as many lion as zebra or wildebeest in the Serengeti. Top predators such as great white sharks, and lions or tigers cannot be all that common relative to their prey, or they would run out of food.
Apex predators are normally between a third and a quarter of their favourite prey numbers because they need much more energy in order to hunt. There were just too many T. rex in the Cretaceous to have subsisted on a diet of large herbivores. 'They were opportunists, eating everything they could find,' said the lead palaeontologist on the project, Jack Horner at the Museum of the Rockies in Bozeman, Montana, 'T. rex was much more like a hyena, an opportunistic hunter which will eat almost anything, dead or alive.'
The extensive survey of the 1000km2 Hell Creek formation took place over a decade, between 1999 and 2009, but work will continue into summer 2011 to remove the last specimens from the ground. Its purpose was to look at the relative abundance of the various dinosaur species there. Everything was collected from plants to turtles and mammals, as well as the dinosaurs. The fossils date from a time between 65 and 95 million years ago when the area was on the borders of an inland sea that would expand and contract over the coastal plains depositing sediments that were later exposed and heavily eroded to reveal the animals that had become trapped.
'The absence of juvenile Tyrannosaurus at the sites is expected as most dinosaurs had specific nesting grounds, but what is surprising,' explained Horner, 'is just how rare the very biggest adults are. It means that there is a high mortality rate during sexual maturity, and we do not yet know why that was.'