Jack Horner

[Shroom Man 777]

The guy who keeps on insisting T-rex is a scavenger. Err, could anyone tell me how valid his claims are? I've heard that he actually doesn't specialize on the Rex, studying Maiasauruses and other pussy dinosaurs and their behaviours instead, making noise about Rex just to gain publicity. Is this troo?

[Greymalkin]

From what I remember, Honer has a good reputation and is considered to know what he is talking about. Of course I haven't studied this kind of stuff in a long time. And despite the fact that I attended the college he works for, Montana State University (in truth Honer is about the only reason MSU has a paleo program and he does bring a considerable prestige to what is otherwise a small school in Montana) and frequented the Museum of the Rockies, I know relatively little about him or his research. After all, I studied Art, not paleontology.

I knew several people that were in MSU's paleo program, one of them did not like him in any way. She felt that he was an "arrogant fuckhead", yes that is a quote, of course so was she.

Here are some articles on it, I hope they help -

T. rex: Scavenger or Predator?
A current topic in paleontology that has received much popular press is the question of whether T.rex (or other Tyrannosauridae in general) were predators or scavengers. Let's explore this issue.

Paleontologist Jack Horner of the Museum of the Rockies (Bozeman, MT) has proposed that T.rex could not have been a predator. His arguments against predation include its small eyes (needed to see prey), small arms (needed to hold prey), huge legs (meaning slow speed) and that there is no evidence for predation — bones have been found with tyrannosaur teeth embedded in them or scratched by them, but so far no study has shown that tyrannosaurs killed other dinosaurs for food (a bone showing tyrannosaur tooth marks that had healed would be strong evidence for predation).

His evidence supporting scavenging include its large olfactory lobes (part of the brain used for smell), and that its legs were built for walking long distances (the thigh was about the size of the calf, as in humans). Vultures have large olfactory lobes and are good at soaring to cover long distances.

There are arguments against scavenging. Most large living predators (such as lions and hyenas) do scavenge meat happily when it is available, but most do prefer fresh meat. Horner argues that its arms were too weak to grab prey, but sharks, wolves, snakes, lizards and even many birds are successful predators without using their forelimbs (if any). Whether T.rex was a slow animal is tough to tell, as our dinosaur speeds page will tell you.

What is the public to think of all this? It is suggested that you make up your own mind; the fact is that reconstructing the behavior of extinct animals is difficult, especially when there are no close modern relatives with which to compare them. Tyrannosaurs may have been scavengers, predators or both; Horner is merely presenting an opposing argument that shows that we are not yet 100% sure what ecological niche the great tyrannosaurs filled.

An article from the BBC.

The website for the Museum of the Rockies.

[salm]

I just saw some show on TV in which it was shown that a T-Rex probably attacked a Triceratops.
The Triceratops had holes in his bones which mached the teeth of the T-Rex. But the bones grew together again, meaning that the T-Rex must have attacked a living Triceratops.

[GrandMasterTerwynn]

The guy who keeps on insisting T-rex is a scavenger. Err, could anyone tell me how valid his claims are? I've heard that he actually doesn't specialize on the Rex, studying Maiasauruses and other pussy dinosaurs and their behaviours instead, making noise about Rex just to gain publicity. Is this troo?

Like most top predators, tyrannosaurs probably weren't above the odd bit of kill stealing or scavenging. One likes to think of modern-day lions as these fantastic hunters, which they are. However, if given the opportunity, they'll chase other predators off their kills.

Horner's claims that T-Rex had some adaptations which might've been useful for scavenging are perfectly valid. T-Rexes could bite through bone with their formidable teeth, and a brain with fairly enlarged olfactory lobes, giving it an equally formidable sense of smell.

There is also the problem of T-Rex not being able to move that fast. Recent studies show that T-Rex couldn't move much faster than about 11 MPH (18 km/h) and fossil evidence (dinosaur tracks) seems to confirm this. However, T-Rex still moved faster than the species of dinosaur it's been known to eat, and it breathed like a bird (via a system of air sacs. It's extremely efficient,) so could likely keep up this pace for a very, very long time. Also, T-Rex apparently had large eyes, and evidence exists for large optic nerves, so it could probably see pretty well.

Furthermore, fossil evidence directly contradicts the "T-Rex as a pure scavenger" theory. At least one hadrosaur (T-Rex prey animal) has been found bearing bone injuries inflicted by T-Rex teeth. However, these injuries appear to have healed, indicating that the animal was attacked while it was alive, and managed to get away to tell the tale.

So, really, the picture that emerges of the T-Rex is that of a typical top-predator. Which is to say that, yes, they did hunt. But yes, they probably weren't above scavenging.

[Shroom Man 777]

Hey, I was never saying it never scavenged. That would be stupid.

(a bone showing tyrannosaur tooth marks that had healed would be strong evidence for predation).

PWNED!

Vultures have large olfactory lobes and are good at soaring to cover long distances.

But they don't grow up to be the biggest carnivores around, and neither do they bully lions or hyenas or other predators off their kill. Is there any scavenger that is able to bully predators off their kill? I mean, aside from lions, since they too are predators. I don't think there's an example of a pure specialized scavenger bullying top-predators.

Hey, and if T-rex was a scavenger, then who was top-predator? Intsy-bitsy dromeosaurids? Utahraptor descendants?

[RedImperator]

Horner has never explained exactly who was the top predator in the late Cretaceous if it wasn't T. Rex. Something had to be eating those hadrosaurs and ceratopsians (which just happened to reach their largest size at the same time the tyrannosaurs did). The other tyrannosaurs all share the same features as T. Rex, so his objections to Rex as a predator should apply to them as well. The only other candidates are the dromeosaurs, but there's no evidence they could take down the big herbivores.

[starfury]

The guy who keeps on insisting T-rex is a scavenger. Err, could anyone tell me how valid his claims are? I've heard that he actually doesn't specialize on the Rex, studying Maiasauruses and other pussy dinosaurs and their behaviours instead, making noise about Rex just to gain publicity. Is this troo?

Seem to be, as stated before if T-rex is not top predator something else must keep the herberivoes in check and the rest are all pussy raptors.

sure it is not above scavenging, but to suggest that it evolved all these features purely for scavenging is bull, I always thought nature was very conservative, if a trait existed that is in excess of what is needed it is ususally lost.

[Shroom Man 777]

And those raptors have a hard time with itsy bitsy protoceratops.

If utahraptor (which was not a pussy raptor) survived up to Rex' time, or if there were utahraptor-sized raptors and not just the teeny weenie velociraptors, would they be able to keep the herbivores in check? Aren't they big enough to take on large herbivores?

The other tyrannosaurs all share the same features as T. Rex, so his objections to Rex as a predator should apply to them as well.

I heard on a documentary that juvenile Rexes could run pretty fast, and they thought that the juvies would run around and chase prey and route them to the bigger adults who would ambush the prey. Maybe the smaller tyrannosaurids could also do this (well, the chasing part, not the leading them to adult Rex ambushes)?


Oh, and I've read that another reason for Horner to believe Rexes are scavengers is that they may work together in packs. What the?

[Akhlut]

There is also the problem of T-Rex not being able to move that fast. Recent studies show that T-Rex couldn't move much faster than about 11 MPH (18 km/h) and fossil evidence (dinosaur tracks) seems to confirm this.

I thought there was only one set of Tyranosaurid tracks in existence. Have more been found? I could understand if they based that figure off of leg length and what not, but I'd think the number would be kind of suspect if it were based on a single datapoint.

However, T-Rex still moved faster than the species of dinosaur it's been known to eat, and it breathed like a bird (via a system of air sacs. It's extremely efficient,) so could likely keep up this pace for a very, very long time. Also, T-Rex apparently had large eyes, and evidence exists for large optic nerves, so it could probably see pretty well.

It also may not have needed to move that fast even if its prey could move a bit faster than it; if it were like the Komodo dragon (mouth filled with deadly, infectious bacteria), then it would only need to get one bite in and let septicemia take the animal down. From there, it could use it's long-distance walking and superb sense of smell to track down it's now dead prey.

Furthermore, fossil evidence directly contradicts the "T-Rex as a pure scavenger" theory. At least one hadrosaur (T-Rex prey animal) has been found bearing bone injuries inflicted by T-Rex teeth. However, these injuries appear to have healed, indicating that the animal was attacked while it was alive, and managed to get away to tell the tale.

Has Horner addressed that particular fossil?

[Majin Gojira]

Honor, IIRC, is the guy basically taking the devil's advocate rout, in order to counter a lot of T-Rex wank that had accumulated. T-Rex was likely a predator, but not to the levels that are often ascribed to him.

As for Other predators, IIRC, at certain points in time, they co-existed with Dromeosaurs, Troodontids and Albertasaurs (smaller, lighter version of Rex's).

[Drooling Iguana]

If there were any Utahraptors around in T-Rex's time, I think they would be too busy arguing with said T-Rex about his constant stomping of things to do a lot of hunting.

[Darth Raptor]

It's impossible for a warm-blooded animal of such incredible mass to be a full-time scavenger. The only endotherms that are full-time scavengers can do so because they can fly- covering vast amounts of territory in a short amount of time. If we're talking about the late, late Cretaceous in North America (Maastrictian) T. rex was most certainly the top predator. The dromaeosaurs of Hell Creek and other places were rather smallish. Albertosaurus was already extinct, and T. rex walked on the fossils of Utahraptor.

Horner also says that dinosaurs died from diseases they were susceptible to because of a genetic bottleneck- before the Alvarez Meteor even hit. But that's what you get from someone who specializes in North American hadrosaur eggs. The giant land vulture hypothesis is just grandstanding. Pay it no mind.

[wolveraptor]

I read a book by Horner once, and in it, he explained that he didn't really believe that T. rex was a pure scavenger; he just liked to take the position in debates to counter those who saw the creature as a shimmering god of hunting. His real position was that T. rex was an opportunist, scavenging when it could and hunting when it couldn't.

Certainly, it must have been the top predator of its time. Theories that raptors were are ludicrous, as dromaeosaurids had diminished in size as the tyrannosaurids grew (from Utahraptor to Deinonychus to Velociraptor).

[Majin Gojira]

Also, recent evidence suggests that Raptors didn't slice up bellies like we believed, but stabbed with their toes--into the jugular veins of their prey.

[Surlethe]

Also, recent evidence suggests that Raptors didn't slice up bellies like we believed, but stabbed with their toes--into the jugular veins of their prey.

Raptors just gained +15 in my eyes for being totally badass. Stabbing toeclaws into jugulars is even more motherfucking badass than ripping up bellies and disembowling.

About T. rex' hunting ability -- what is the postulated hadrosaur top speed?

[Darth Raptor]

About T. rex' hunting ability -- what is the postulated hadrosaur top speed?

I'm afraid that would depend on the species. The Hadrosauridae ran the gamut between semi-bipedal and fully quadrupedal forms. It should be noted that since their forelimbs were reevaluated it's now clear that ceratopsians- Triceratops in particular- were desperately slow.

As mentioned earlier in this thread, juvinile tyrannosaurs were far more gracile than their adult counterparts. If dumber theropods like allosaurs and megalosaurs can hunt in packs, I don't see why rexes couldn't prowel in hordes.

[wolveraptor]

Also, recent evidence suggests that Raptors didn't slice up bellies like we believed, but stabbed with their toes--into the jugular veins of their prey.

How on earth could they tell that?

On juvenile Tyrannosaurids: I believe a fossil was discovered rather recently of a young tyrannosaurid (or possibly a different species altogether, though that's unlikely). It was called "Jane", and it was at first considered to be a completely different species to the extreme differences in gracility and slenderness as compared to adult T. rexes. It is believed this difference in morphology came about in an attempt to prevent the overlapping of diets by young and adults, which would lead to competition. Gracile t. rexes would hunt faster and smaller hadrosaurids, while the larger, bulkier adults would feast upon ceratopsians.

[RedImperator]

Interesting note: Horner has apparently never proposed his "scavenger T. Rex" theory in any scientific publication. He's very much just making noise to de-wank Rex a bit.

[Elfdart]

It's impossible for a warm-blooded animal of such incredible mass to be a full-time scavenger. The only endotherms that are full-time scavengers can do so because they can fly- covering vast amounts of territory in a short amount of time. If we're talking about the late, late Cretaceous in North America (Maastrictian) T. rex was most certainly the top predator. The dromaeosaurs of Hell Creek and other places were rather smallish. Albertosaurus was already extinct, and T. rex walked on the fossils of Utahraptor.

Agreed. Vultures, condors and similar scavengers use very few calories because they float on updrafts of warm air. That's why they seldom fly at night. Walking, let alone running burns an exponentially larger number of calories. There's a reason why there's no such thing as a terrestrial scavenger.

Horner also says that dinosaurs died from diseases they were susceptible to because of a genetic bottleneck- before the Alvarez Meteor even hit. But that's what you get from someone who specializes in North American hadrosaur eggs. The giant land vulture hypothesis is just grandstanding. Pay it no mind.

The genetic bottleneck is accurate. Compare the variety of species at the K-T boundary and the layers a few million years older. It's like comparing the fauna of today's southwestern US to that of 12,000 years ago. Speaking of which...

Also, recent evidence suggests that Raptors didn't slice up bellies like we believed, but stabbed with their toes--into the jugular veins of their prey.

Raptors just gained +15 in my eyes for being totally badass. Stabbing toeclaws into jugulars is even more motherfucking badass than ripping up bellies and disembowling.

About T. rex' hunting ability -- what is the postulated hadrosaur top speed?

No surprise there. The claws of dromaeosaurs resemble the canines of sabretooth cats and most likely were used in the same manner: puncturing and simultaneously cutting the jugular all in one motion. In the Middle East and Central Asia, herdsmen use a curved dagger in the exact same way when killing sheep or goats. The curved blade makes it less likely to catch on the neck bones and if the non-sharpened edge contacts the bone, it forces the sharpened edge down -becoming a kind of lever.

The velociraptor's claws were also ideally suited for climbing trees, much like the climbing spikes used by phone repairmen. I suspect they may have climed trees and pounced on their prey from above like cougars and leopards have been known to do (the dromaeosaurs -phone repairmen attack their prey when they mail out the phone bill) . This would give their claws even more cutting power as their full body weight plus gravity would literally kick in.

[Darth Raptor]

The genetic bottleneck is accurate. Compare the variety of species at the K-T boundary and the layers a few million years older. It's like comparing the fauna of today's southwestern US to that of 12,000 years ago. Speaking of which...

The reason for the decline in Maastrichtian diversity is the extremely toxic amounts of volcanism that were going on at the time. There's no reason to assume that dinosaurs were in a similarly bad way elswhere on the planet. Even if the North American ecosystems were totally destroyed, they would have been replaced by migrant communities from Asia or South America once the habitat recovered. This continent has always been a volcanic death trap- but when that's all you know from the end of the Cretaceous, it falaciously paints a picture of a Dinosauria already on their way out when the Alvarez Meteor hit.

[starfury]

No surprise there. The claws of dromaeosaurs resemble the canines of sabretooth cats and most likely were used in the same manner: puncturing and simultaneously cutting the jugular all in one motion. In the Middle East and Central Asia, herdsmen use a curved dagger in the exact same way when killing sheep or goats. The curved blade makes it less likely to catch on the neck bones and if the non-sharpened edge contacts the bone, it forces the sharpened edge down -becoming a kind of lever.

The velociraptor's claws were also ideally suited for climbing trees, much like the climbing spikes used by phone repairmen. I suspect they may have climed trees and pounced on their prey from above like cougars and leopards have been known to do (the dromaeosaurs -phone repairmen attack their prey when they mail out the phone bill) . This would give their claws even more cutting power as their full body weight plus gravity would literally kick in.

Not Surprising, since it was the raptor's body plan seem closet of that of the Big Cats like the Sabertooth, with a less of emphasis on running and a on the grabbing and biting look.

The tyransoaurs seem closer to hyenas in killing function, relative fast runners which killed which their mouths, as I recall some of those old hyendons were as big as rhinos.

[Darth Raptor]

Not Surprising, since it was the raptor's body plan seem closet of that of the Big Cats like the Sabertooth, with a less of emphasis on running and a on the grabbing and biting look.

Dromaeosaurs were most certainly built for running- just a different kind of running than other fast dinosaurs like hypsilophodonts or ornithomimids. While the herbivorous bipeds were endurance runners- taking a relatively long time to reach top speed and maintaining that long enough to outlast any pursuer (think ostrich), raptors were sprinters- their relatively short, muscular legs enabled them to reach top speed very quickly, but they tire out over short distances (think cheetah).

The tyransoaurs seem closer to hyenas in killing function, relative fast runners which killed which their mouths, as I recall some of those old hyendons were as big as rhinos.

The majority of large, carnivorous theropods killed with their mouths- and T. rex is no exception- barring the long, serrated teeth for the job. The difference is that allosaurs and megalosaurs- which specialize in killing things larger than them had a "hit and run" approach to killing. They would run in, take a large, hemmorhagic bite out of their prey and run out for another pass. Rex, on the other hand, killed things the same size as itself or smaller. Few theropods had such immense bone-crushing jaw power as Tyrannosaurus. A tyrannosaur would charge in and absolutely destroy its prey in a single attack. A powerful, ambush predator like that doesn't really need to be a runner. But even analogous mammals like the Andrewsarchus you mention aren't immune to this land vulture crap. Although some of the giant mesonychids could have been omnivorous.

[Elfdart]

The genetic bottleneck is accurate. Compare the variety of species at the K-T boundary and the layers a few million years older. It's like comparing the fauna of today's southwestern US to that of 12,000 years ago. Speaking of which...

The reason for the decline in Maastrichtian diversity is the extremely toxic amounts of volcanism that were going on at the time. There's no reason to assume that dinosaurs were in a similarly bad way elswhere on the planet. Even if the North American ecosystems were totally destroyed, they would have been replaced by migrant communities from Asia or South America once the habitat recovered. This continent has always been a volcanic death trap- but when that's all you know from the end of the Cretaceous, it falaciously paints a picture of a Dinosauria already on their way out when the Alvarez Meteor hit.

Major volcanic eruptions can affect life on the other side of the planet like the Little Ice Age of the early 1800s or the Three Year Winter of 540-543 AD -both of which were caused by eruptions in Indonesia.

[wolveraptor]

The velociraptor's claws were also ideally suited for climbing trees, much like the climbing spikes used by phone repairmen. I suspect they may have climed trees and pounced on their prey from above like cougars and leopards have been known to do (the dromaeosaurs -phone repairmen attack their prey when they mail out the phone bill) . This would give their claws even more cutting power as their full body weight plus gravity would literally kick in.

Since the second toe claw in their possible ancestor Archaeopteryx was likely used for climbing, this is not unlikely.

[lgot]

Interesting note: Horner has apparently never proposed his "scavenger T. Rex" theory in any scientific publication. He's very much just making noise to de-wank Rex a bit.

Yes, My brother and I are members of a emailing list of paleontologists (well, more my brother) and a few years ago someone asked about this and a member posted his public speech in his university saying that was a red flag he waved to get attention and new debates (and money) in the media.