The tyrannosaur family that preyed together, stayed together. That is the conclusion of University of Alberta paleontologist Philip Currie after examining the remains of numerous tyrant dinosaurs in Alberta and Mongolia over the past thirteen years. Instead of being solitary hunters, Currie proposes, fearsome predators such as Tyrannosaurus rex and its close relative Tarbosaurus bataar hunted in coordinated packs in which hunters both young and old had their own distinct roles to play.
The notion of pack-hunting dinosaurs is not new. In the 1970s Yale paleontologist John Ostrom hypothesised that Deinonychus – the sickle-clawed carnivores that were the model for Jurassic Park's Velociraptor gang – worked in co-operative packs on the basis of multiple individual specimens found in association with the prey species Tenontosaurus. Two decades later, Currie proposed that the large tyrannosaur Albertosaurus might have co-operatively run-down other dinosaurs on the basis of a huge Albertosaurus bonebed at Dry Island Buffalo Jump Provincial Park, Canada. In a 2000 paper titled "Possible evidence of gregarious behaviour in tyrannosaurids", Currie hypothesised that the Albertosaurus quarry preserved the remains of a family group in which the younger, faster animals drove terrified prey towards the waiting mouths of the more powerful adults. (In two subsequent papers, Currie also suggested family lifestyles for another tyrannosaur, Daspletosaurus, and a very distantly-related predatory dinosaur from South America named Mapusaurus.)
With the release of the book and documentary "Dino Gangs", though, Currie has forwarded Tarbosaurus skeletons from Mongolia as additional evidence for his ideas. The essential, precise details of the sites Currie investigated with the Korea-Mongolia International Dinosaur Project between 2006 and 2010 have not yet been released – no scientific paper has been published on the site in question – but Currie believes that he has found a bonebed containing several individuals of Tarbosaurus which echoes the story of the Canadian Albertosaurus quarry. These tyrannosaurs, in his view, represent a cooperative group. He also cites the lighter build of juvenile tyrannosaurs and the brain anatomy of these dinosaurs as being consistent with the idea that Tarbosaurus was a pack-hunter.
But there are many ways to make a bonebed. Determining whether all the animals in a bonebed died simultaneously or accumulated over a longer time period is a difficult task, and it is even more difficult to figure out whether animals buried together represent a social group or an aggregation brought together by other causes. Just because skeletons are found in close association does not mean that the animals were living together or were cooperating with each other before they died, especially since local catastrophes – such as drought or flooding – can bring animals into close quarters before killing them. For these reasons other paleontologists, such as Currie's colleague David Eberth at Alberta's Royal Tyrrell Museum, have raised serious doubts about whether the tyrannosaur bonebeds truly indicate gregarious behavior among the dinosaurs. In order to figure out how the dinosaurs lived, the intricate details of their deaths – how and when they perished – must first be ascertained. Perhaps Tarbosaurus, Albertosaurus, and their kin really did hunt together, but the conclusive evidence for "Dino Gangs" has not yet been found.
A team of dinosaur experts will take part in a live webchat at 1pm 22 June 2011. The panellists are:
Dr Philip Currie, a Canadian paleontologist and museum curator who helped found the Royal Tyrrell Museum of Palaeontology in Drumheller, Alberta and is now a professor at the University of Alberta in Edmonton. In the 1980s he became the director of the Canada-China Dinosaur Project and helped describe some of the first feathered dinosaurs. He is one of the primary editors of the influential Encyclopaedia of Dinosaurs, and is an expert on theropods (especially Tyrannosauridae), the origin of birds, dinosaurian migration patterns and herding behaviour.
Brian Switek, author of Written in Stone: Evolution, the Fossil Record, and Our Place in Nature. Brian also writes for the WIRED science blog Laelaps and Smithsonian magazine's Dinosaur Tracking as well as The Guardian and The Times.
David Orr, editor of Love in the Time of Chasmosaurs, a blog dedicated to dinosaur science and pop culture.
The chat will be live on the Discovery Channel UK Facebook page 1pm today.
• A documentary on Dr Currie's research, Dino Gangs, will air on the Discovery channel on Sunday 26 June at 9.00pm