Tyrannosaurus - pack hunter?

http://http://www.newscientist.com/blogs/culturelab/2011/06/did-dinosaurs-hunt-in-packs.html


A few weeks ago, two UK palaeontologists announced the discovery of the world's tiniest dinosaur. The diminutive species was just 33 to 44 centimetres in length and weighed around 200 grams - all of which the pair worked out from a single vertebra. It's just one example of how a skilful palaeontologist can see the big picture - or in this case the little picture - from what most of us would view as the scrappiest of data.

Philip Currie at the University of Alberta in Edmonton, Canada, knows all about squeezing information out of relatively unpromising starting material. He has spent the last 15 years chipping away at an impressively bold hypothesis: that the tyrannosaurs hunted in packs rather than alone, making them even more formidable than we had thought. The hypothesis gets a thorough examination in Dino Gangs, a 2-hour documentary that airs on the Discovery Channel in the UK this Sunday. (Currie also co-wrote an accompanying book by the same name.)

This is controversial stuff, but happily the documentary makers give the sceptics a voice - several leading palaeontologists explain exactly why Currie's idea has yet to convince many in the community. Fundamentally, they say, working out anything meaningful about how a long-dead animal behaved 70 million years ago is always going to be tricky.

But Currie isn't daunted. Early on we're told that the most convincing supporting evidence would come in the form of a tyrannosaur mass grave - shattering the consensus view of the beasts as solitary animals. And Currie comes up trumps: not only does he find 23 tyrannosaurs buried together in Canada, but he also explores a site in the Gobi desert where no less than 68 tyrannosaurs have been found within spitting distance of one another.

But then the wheels begin to come off. A geological analysis of the Gobi site suggests the skeletons there were deposited over hundreds of thousands of years - that their geographical proximity is just a quirk of prehistory. And things get worse: a sceptical palaeontologist tells us that even finding multiple tyrannosaurs buried together isn't enough. The dino gang hypothesis rests on evidence of multiple tyrannosaurs at a kill site - something yet to be found.

Fieldwork in the Gobi desert, Mongolia (Image: Discovery Channel)

Undeterred, Currie turns to modern predators in his quest for convincing evidence, and in the process we visit such exotic locations as Indonesia (for its Komodo dragons), South Africa (for its lions)... and England, home not to giant predators but to an impressive motion capture studio which helps establish that young tyrannosaurs were twice as swift as the bulky adults. Did the two team up to hunt as lions do?

What's clear is that Currie - and the documentary makers - have given serious thought to the dino gang hypothesis. If slick, big-budget presentation was enough to persuade, we'd have a winning theory 90 minutes into the show. But it's not, and the sceptics remain unmoved.

Currie's final throw of the dice is X-ray scans of a tyrannosaur skull, which show its brain was six times bigger than any other dinosaurs alive at the time. Is this the clincher? "I wish we could point to a cooperative hunting lobe of the brain - sadly it doesn't really work that way," says Larry Witmer at Ohio University in Athens, who helped Currie perform the scans. Currie and Witmer do, at least, decide that there's nothing in the tyrannosaur brain to suggest it was incapable of cooperation. Needless to say, others disagree.

But we've no time for a riposte from Currie, although we are treated to a curious epilogue that suggests a better understanding of dinosaur behaviour could prove informative for understanding our own destructive ecological behaviour.

The impressive, if speculative, evidence Currie has already amassed is presented in an easy to follow form in Dino Gangs, complemented with the obligatory Jurassic Park-like CGI animations. But the lasting impression is of a jigsaw with its final, vital piece missing. The great thing about science, though, is that it doesn't end when the credits roll. That final piece is always just a fossil away. And while we wait for Currie to find it, there are certainly worse ways to kill 2 hours.

Dino Gangs premiers on the Discovery Channel in the UK at 9pm Sunday 26 June

Got the impression that it was aimed at a younger audience. Nothing new in what was said, and calling dinos by their wrong names got annoying.


The same show could have been done in 45mins and been a far better watch.

Adam Khor wrote: »

Hadrosaurs were not defenseless. They weren´t slow (they were recently confirmed to have been fast runners, which is the only thing that makes sense considering who was chasing after them), and they had heavy, powerful tails that could be used to hit predators. According to some paleontologists I talked too, the edges of hadrosaur's beaks weren´t as nice and soft as they look in most reconstructions; they had keratinous edges that were very sharp and sometimes even serrated, meaning they probably could bite if necessary. I'm not saying they were equiped to fight with a T-Rex the way a Triceratops would, but they weren´t all helpless either.

As for the pack-hunting theory, I can see it work for other smaller carnivorous dinosaurs, but not T-Rex. It was way too big, and unlike carcharodontosaurs which seem to have been specialized sauropod hunters, T-Rex was feeding on prey its own size or smaller.

Even an adult Edmontosaurus or Triceratops wouldn´t be large enough for a whole pack of hungry Tyrannosaurus. The bigger, stronger ones would probably eat most of the kill and leave the smaller weaker members hungry. If we consider that the smaller members of the pack would probably be the ones chasing prey at high speed (as they would be faster than their biggest pack mates), it would be a tremendous energy waste.

Sure, some modern day predators like lions hunt in packs, and yes, the biggest ones (the males) monopolize the kill until they're full, but, let's consider that lions often prey on animals much bigger than themselves. Even if sometimes the lionesses and cubs go hungry, there's always the possibility of taking down a Cape Buffalo, or a zebra and have a satisfying meal for everyone.

The only animal I can think of big enough to feed a pack of several adult T-Rex would be an Alamosaurus, but a) it seems to have been rare, b) it was way too big to be targeted often, c) there's plenty of evidence that T-Rex preyed mostly on hadrosaurs and ceratopsians, and d) Alamosaurus seemingly wasn´t very widespread.

It just makes a lot more sense, to me anyways, if T-Rex was a lone hunter, or at most, if it hunted in pairs, like some birds of prey do today.

Would lean towards the bird of prey comparison as well.

My own take is that the adults would have hunted seperately for a fair chunk of the time, but possibly hunted as a pair or as a loose pair during the breeding season and after the Rex younglings "fledged".

I spend a lot of time observing birds of prey, especially sparrowhawks as I have been lucky enough to have had a regular female who has nested on my land for a few years now, and when the young fledge it is not unusual to see the young travelling together or to see them following the male and watching/learning.

I have also observed on a number of occasions the two adults working in manner that would suggest cooperation, but only during the breeding season.

T Rex doing something similar makes a lot of sense to me, with the young probably staying with the female until they are capable of catching and killing prey in their size bracket.



I have a theory that modern raptors offer the best clue as to how theropods hunted with the majority of raptors being lone hunters outside of the breeding season or at most , but the fly in the ointment would be the Harris Hawk. A medium sized raptor that can hunt very well alone but also pack hunts when there is a need to take down larger prey. Interestingly enough the Harris Hawk, when pack hunting, shares food quite well as a group with anything from 2 to 8 birds taking part in such activities. For my money the Harris hawk's behaviour is probably quite similar to the behaviour of the various dromaeosaurids, something that most would believe anyway, but the sparrowhawk behaviour is my best bet as to how the medium to large sized theropods interacted. I am using sparrowhawks as an example because as well as them being a very adaptable predator that will and can change it's ambush strategies within minutes of an obstruction presenting itself, they are a species that we here in Ireland can view on a regular basis in the countryside and in sub urband/Urban areas all over the country.

Adam Khor wrote: »

I know the Harris Hawk very well; I've seen it and photographed it in the wild.

Lovely bird isn't it?

Which sub species did you photograph? Seen them in the wild in North America and have handled falconry Harris Hawks over here and in the UK.

Adam Khor wrote: »

P. u. harrisi :>

Where were you observing them? Mexico?