Tyrannosaurus rex tooth in a hadrosaur: The scavenger vs. predator debate is over.

Tyrannosaurus rex Is Done Answering Questions About Its Diet

Tyrannosaurus rex Is Done Answering Questions About Its Diet

The state of the universe.
July 17 2013 1:00 PM

Stop Asking Tyrannosaurus Rex About Its Diet

Can’t a carnivorous dinosaur just eat whatever it wants to?

Dinosaur Sue, the largest intact Tyrannosaurus Rex specimen yet discovered, is prepared for display at the Dinosaur Expo at the National Science Museum in Tokyo, Japan, March 14, 2005.
Dinosaur Sue, the largest intact Tyrannosaurus Rex specimen yet discovered.

Photo By Toshifumi Kitamura/AFP/Getty Images

This week I encountered the question that, as a scientist who has studied a certain chunky Cretaceous carnivore a lot, most deflates me and makes me want to go study cancer therapeutic methods or energy sources that are alternatives to fossil fuels (but I’d be useless at either). I will explain why this is at the end of the post.

The question is whether Tyrannosaurus rex was a predator or a scavenger. It stems from a new discovery reported in the Proceedings of the National Academy of Sciences and thus expected to be one of the more important or exciting studies this year. (No, I’m not going to get into the issue here of whether these “high impact” journals include the best scientific research or the most superficial or hyped “tabloid” science; they publish both, and not in mutual exclusivity.) It’s a broken Tyrannosaurus rex tooth embedded in a duckbill dinosaur’s tail bone, which healed after the injury, showing that the animal survived the attack.

If you’re with me so far, you might be making the logical leap that this fossil find is then linked to the hotbed of furious controversy that still leaves paleontology in crisis almost 100 years after the paleontologist Lawrence Lambe suggested it for the tyrannosaur Gorgosaurus. If the hadrosaur survived an attack from a T. rex, then T. rex was a habitual predator and OMG Jack Horner and others before him were wrong!

And you’d be right.

My encounter with the question stemmed from an email from a science journalist, Matt Kaplan, who, as is normal practice, shared a copy of the unpublished paper and asked for comments from me to potentially use in an article he was writing for the science journal Nature’s news site. Here, then, was my off-the-cuff response:

“Ooh. I do have a pretty strong opinion on this. Not sure if you’d want to use it but here goes. I may regret it, but this hits my hot buttons for One of the Worst Questions in All of Paleobiology!

The T. rex ’predator vs. scavenger‘ so-called controversy has sadly distracted the public from vastly more important, real controversies in paleontology since it was most strongly voiced by Dr. Jack Horner in the 1990s. I find this very unfortunate. It is not like scientists sit around scratching their heads in befuddlement over the question, or debate it endlessly in scientific meetings. Virtually any paleontologist who knows about the biology of extant meat-eaters and the fossil evidence of Late Cretaceous dinosaurs accepts that T. rex was both a predator and scavenger; it was a carnivore like virtually any other kind that has ever been known to exist.

While the discovery is nice evidence, it is not particularly exciting in a scientific sense and is only one isolated element from species that lived for hundreds of thousands of years, which to me changes nothing and allows no generalizations about the biology of any species, only the statement that at one point in time a Tyrannosaurus bit a hadrosaur that survived the encounter. There is no real substance to the controversy that T. rex was ’either‘ a predator or scavenger. It is just something that scientists drum up now and then to get media attention. I hope that soon we can move on to more pressing questions about the biology of extinct animals, but the media needs to recognize that this is just hype and they are being played in a rather foolish way; likewise scientists who still feel this is an exciting question need to move on. Maybe this specimen will allow that. But somehow my cynical side leads me to suspect that this ’controversy‘ will just persist because people want it to, regardless of logic or evidence.

Great galloping lizards, I am so tired of this nonsense. Maybe there is educational value in showing how science deals with provocative half-baked ideas about celebrity species, but scientists in the community need to speak up and say what the real science is about. It’s not about this 'controversy.’ Modern paleontology is so much better than this.

Sorry for the rant. Maybe it’s too extreme, but I’m just fed up with this non-issue! I suspect a huge proportion of our field feels similarly, however.”

(I later redacted a bit of it where I got a little too excited and used the word curmudgeon; a mistake, as that could be seen as ad hominem rather than a term of endearment, and this issue is about the science and not the people, per se. That bit is redacted here, too. I’ve also redacted a sentence in which I made an opinion on whether the paper should have been published in PNAS; that is mostly irrelevant here. I was not a reviewer, and authors/reviewers/editors have to make that decision. This would be a massive tangent away from what this post is intended to be about! I know some of the authors and don’t want to offend them, but this is about the science and how it is represented to the world, not about these particular authors or even this paper itself.)


Importantly, Kaplan’s story did include my skeptical quote at the end. I am curious to see how many other news stories covering this paper go that far. [Ed. note—Embarrassingly, a Slate Trending News Channel video did not.]

I will stop right here and acknowledge that I’ve published a lot on a somewhat related topic: how fast a T. rex could run or whether it could run at all. To me, that’s a great scientific question that has consequences not only for the predator/scavenger false dichotomy, but also for general theories of locomotor biomechanics. (Can an animal the size of a large elephant run as well as or better than said elephant? What are the thresholds of size and maximal running/jumping/other athletic abilities and how do they vary in different evolutionary lineages? And so on.) I’ll defend the validity of that question to the bitter end, even if it’s a question I’ve grown a little (but only a little) tired of and generally feel is about as well settled as these things can be in paleontology (see my review here). I’ll also defend that it has been a real controversy (I have plenty of old emails, formal rebuttals submitted by colleagues, and other discourse as evidence of this) since I tackled it starting in 2002 and sort of finishing by 2011. I am sensitive about the issue of hyping my research—this is something I’ve been careful about. I set a reasonable bar of how much is too much, check myself continuously with reflective thought, and I do not feel I have ever really crossed that bar, away from science-promotion into darker realms. This is partly why I’ve stopped addressing this issue in my current work. I feel like the science we’ve done on this is enough for now, and to keep beating the same drum would be excessive, unless we discovered a surprising new way to address the questions better, or a very different and more compelling answer to them.

T. rex: scavenger or predator?” was controversial back in 1994 when Horner published The Complete T. rex, where he laid out his arguments that T. rex was a scavenger. Brian Switek covered this quite well in his post on it, so I will not review that history. There was a big Museum of the Rockies exhibit about it that toured the United States, and other media attention surrounding it, so Horner’s name became attached to the idea as a result. Other such as Lawrence Lambe and Paul Colinvaux had addressed it before, but their ideas never seemed to gain as much currency as Horner’s did. But this post is not about that.

What this post is about is a consideration of why this is still an issue that the media report on (and scientists publish on; the two are synergistic of course), since most scientists aware of past debates are in good agreement that a T. rex was like most other carnivores. It was opportunistic as a switch-hitting scavenger-predator, not a remarkably stupid animal that would turn down a proper meal depending on whether it was dead or alive. Indeed, the Nature news piece has a juicy quote from Horner that implies (although I do not know if it was edited or if important context is missing) that he has been in favor of the opportunistic predator-scavenger conclusion for some time. Thus, as Switek’s article notes, even the strongest advocates of the obligate scavenger hypothesis have changed their minds; indeed, that 2011 blog post intimates that this had already happened at least two years ago.


For many years, nothing has been published in the main peer-reviewed literature that favors that extreme obligate scavenger hypothesis. If I am wrong and there is a scientific debate, where are the recent papers (say within the past five years) that are strong, respectable arguments in favor of it? I contend that it is a dead issue. And if it is just about the middle ground—i.e. what percent of its time did a T. rex spend hunting vs. scavenging—we have no clue and may never know, and it’s not a very interesting question. Yes, the new find is a neat fossil. But a different duckbill dinosaur specimen in Denver whose tail a tyrannosaur had reputedly taken a bite out of has been known of for over 15 years , so the novelty of this new specimen is questionable.

But who then is feeding off of this moribund equine; this defunct tyranno-parrot?

In thinking about my reply to the journalist this week, I am reminded again of my general feeling that this is no longer a question of scientific evidence: As I wrote above, the “controversy” may just persist because people want it to, regardless of logic or evidence. Maybe we just like this hypothesis or the controversy, or maybe we’re lazy and don’t want to have to hunt for real debates in science.

But who are “the people”? I do not feel that The Public should be blamed; they are the people that The Scientists and The Media ostensibly are seeking to inform about what the state of modern knowledge and uncertainty is in science. (I really don’t love false capitalization, but I’ll allow it J) So when I get asked about the controversy after a public lecture, I always try to go into detail about it. I don’t sigh and say “go Google it.” Nor do I do this to a journalist. Indeed, I’ve generally headed this issue off at the pass and added a blurb to press releases and webpages explaining my T. rex research to explain how it relates to the non-controversy; example here.


I have to begin turning my finger of accusation away from scientists and toward some of the media, because they must play a huge role in the shenanigans. Yes, scientists should know better than to play this up as a valid, heated, modern controversy. That is true. Yet I have a feeling that the balance of blame should also fall heavily on the side of media (general and science news) that continue to report on this issue uncritically as a real controversy. Thus the general public thinks it still is, and scientists and journals keep issuing papers and press releases implying that it is, leading to more reporting on this supposed controversy, and the beast refuses to die. Switek’s article is a good counter-example of balanced coverage with clear application of critical thinking.

This is trivially different from other non-controversies in paleontology such as whether birds evolved from a subgroup of theropod dinosaurs and hence are dinosaurs by virtue of descent (consensus: yes). So it is reflective of a broader problem of not calling a spade a spade.

And it’s embarrassing, to a scientist, as my quote above expressed, to see dead controversies trotted out again and again, feeding the public perception that they are not dead.

That’s what leaves me frustrated. When do the shenanigans end?


I am reminded of a quote from a Seinfeld episode:

“Breaking up is like knocking over a Coke machine. You can’t do it in one push. You gotta rock it back and forth a few times, and then it goes over.”
Jerry, from the episode “The Voice.”

But this predator/scavenger relationship-from-hell leaves me, as a specialist working in this general area, feeling like I am trapped under that fridge. Help!

That’s why I started off this long post talking about feeling deflated, or disappointed, when asked this question. I do feel that way. I have to admit, I sometimes even feel that way when a sweet young kid asks me that question. Deep inside, I wish they wondered about something else. I wish that science had reached them with a deeper, more contemporary question. But when a journalist asks me how I feel about a new paper that revisits the controversy, I feel embarrassed for paleontology. Can’t we get past this? It makes us look so petty, mired in trivial questions for decades. But we’re not like that. This is a dynamic, exciting, modern field, but every news story about non-issues in paleontology just perpetuates bad elements of paleontology’s image. I am left with some questions:


To the scientists: Why don’t we put our foot down more and say enough is enough, this is a dead issue? We have a role not only in peer review, but also in communicating our views about published work to the media when asked (and when not asked, as in this blog post). But if you call them on it, do they listen? Which brings me to …

To the media: (Science and general journalists and others. I know this is a huge category and please don’t think I am blaming 100 percent of journalists or assuming they are all the same; they are not!) If scientists tell you that a controversy is not such, at what point do you accept their judgment and kill the story, or at least use that quote? Does that ever happen? In what way are you at the mercy of senior editors or others in such issues? What power do you have? Is a shift in the balance of editorial power needed, or even achievable, in your case or in good exemplar cases? I’d really like to hear your experiences and thoughts. I am sure there is a lot I am not understanding, and I know many journalists are in a tough situation.

To the public: You are often being misinformed; you are the losers in this issue. How do you feel about all it? While this post focuses on a very tiny issue, the T. rex scavenger-or-predator unending drama, it is also about a broader issue of how the media perpetuates controversies in science after they have already gone extinct. Yes, we want to get and keep kids and other people excited in science. But is presenting old, tired, well-resolved debates as if they still existed really that good for anyone? There’s tons of cool science out there; why not expect news that is new?

This story originally appeared in John R. Hutchinson’s blog What’s in John’s Freezer?