A mythos has developed that big predators rarely attack big prey, and chow down almost always on juveniles and the infirm. Fortunately I have the volumes by Schaller, Kruuk, Sinclair on lions, hyaenas, cape buffalo oh my. Among gnu attacked by lions 3/4+ were killed by lions when adults. Among zebra over a third were adults in their prime. Same for cape buffalo. Half or more gnu killed by hyaenas were adults. Tigers will go after adult gaurs and moose (Siberia). I have seen many videos of adult big ungulates and ostriches being attacked by lions, tigers, bears, hyaenas, cheetahs, wolves, cape hunting dogs, etc.
A thing about predators is that there are no precision machines programmed to always do what is precisely their best reproductive interest. They are sloppily running animals with emotions that may be subject to wanting to have what we would consider a good time, via taking on big animals for the predatory thrill of it.
As for giant theropods, they lived on danger edge of sudden death. As I explained in my paper in the anniversary of Tyrannosaurus symposium volume, they were small brained, nonnursing, weed-trash r-strategists with very high rates of reproduction and short lifespans just a fraction that of elephants. They were meant to grow fast, broadcast as many eggs as possible, and then die young, probably from predatory combat gone bad. That pattern indicate they took on dangerous prey on a frequent basis.
That out of the limited sample of Triceratops remains that any shows clear signs of engaging in combat with Tyrannosaurus is strong evidence that the latter did go after adults of the former on a fairly regular basis -- if an attack was successful we would not know because unhealed tooth marks can represent either predation or scavenging. If adult Triceratops were rarely attacked then there should be no specimens with evidence of being attacked. If the attacking Tyrannosaurus died in the particular bout described by Happ that is in accord with no known Tyrannosaurus specimen living past ~30.
The Paluxy trackway is too peculiar to be dismissed as merely a giant theropod and sauropod happening to pass the same way. The theropod trail is always immediately to the left of the sauropod, even when the trail of the latter veers to the left. As Thomas pointed out they share the same stride length and cadence, indicating the theropod was matching its speed with the sauropod as can be seen in predator chasing prey videos. At the same spot the trackway veers is where there is a missing footprint of the theropod. The spacing suggests the theropod at the point bit the tail based the sauropod to damage the caudofemoralis, and skipped as it made the contact and was pulled along. At the same point the sauropod shows evidence of stumbling, and its stride length becomes shorter, indicating that it was wounded and its locomotion impaired -- probably one of many assaults made as the theropod tried to disable its prey. That out of the limited sample of sauropod trackways one shows good indications of an attack is evidence that big theropods going after big sauropods was not rare.
Ergo, Tyrannosaurus or a close relation going after adult Alamosaurus on occasion -- maybe a few times in a lifespan of the predator -- is highly plausible. And can be established if healed wounds delivered by big theropods are found on adult sauropods.
I have become very, very skeptical of gigantic yet small brained theropods hunting in packs. Back in the 70s and 80s there were not enough known trackways to test the possibility, but here were are in the 10s and still no trackway showing them moving in groups. Find such trackways and then I shall reconsider.
GSPaul
-----Original Message-----
From: Mike Habib <biologyinmotion@gmail.com>
To: Gregory Paul <gsp1954@aol.com>
Cc: dannj <dannj@alphalink.com.au>; dinosaur-l <dinosaur-l@usc.edu>
Sent: Tue, Jul 2, 2019 4:45 am
Subject: Re: [dinosaur] Fwd: Re: T. rex hunting Alamosaurus
Large predators do attack large healthy adult prey fairly often.Do you have a reference for this? All of the ecology literature I am familiar with indicates that predation on healthy adults is quite rare. Hone and Rauhut (2010) did a nice job of summarizing these modern trends in the context of implications for theropod feeding, specifically, and they concluded that predation on adults was probably rare. It also seems like attacking adults would be rather odd given the sea of vulnerable, mostly unguarded juveniles.From a functional anatomy perspective, theropods donât really seem to have the traits that weâd expect from big prey specialists, either. Iâve noted this before on the list, and it seems to be a deeply unpopular notion for some reason, but I am so far unconvinced by the theropod super predator concept.We know that Tyrannosaurus attacked an adult Triceratops that was healthy enough to survive the attackYes, but the tyrannosaur might not have survived that attack. A major source of mortality for subadult predators in the modern world is poor prey choice leading to injury.It is quite possible that the Paluxy trackway records an acrocanthosaur attacking an adult brachiosaur, possibly by biting its tail base to try to disable leg retractors.Also quite possible that it was merely passing that way and had no intention of trying its luck against something that could murder it easily. Itâs highly speculative either way. Though admittedly fun to consider!General point for this thread: The mechanical performance of large sauropods is chronically underestimated. The poor critters seem to be constantly reconstructed as super sluggish things that could barely move or react. But a kick, neck slam, or tail strike from a sauropod was probably reasonably fast and had a huge reach. I expect that most species were very dangerous when provoked.Cheers,âMBH
-----Original Message-----
From: Dann Pigdon <dannj@alphalink.com.au>
To: dinosaur-l <dinosaur-l@usc.edu>
Sent: Mon, Jul 1, 2019 7:01 pm
Subject: Re: [dinosaur] Fwd: Re: T. rex hunting Alamosaurus
A 6 -10 tonne adult tyrannosaur likely wasn't agile enough to avoid a well-placed kick, tail slap or neck
bump from an adult sauropod either.
The sauropod would not only have the advantage of mass, but also of stability (four legs verses two). A
non-fatal glancing blow from a tyrannosaur would be unlikely to knock a large sauropod over (or even faze
it much), whereas a glancing blow from a large adult sauropod could completely topple a multi-tonne
biped, resulting in an incapacitating injury that might ultimately prove fatal to the predator.
Even if tyrannosaurs attacked as a group, with younger and more agile members harrying the adult
sauropod to exhaustion until the adult tyrannosaurs dared to approach to finish the prey off, there would
still have been the problem of separating the sauropod from its herd members first. Otherwise the
tyrannosaur group would lose their numerical advantage. A sauropod that was already sick or injured in
some way might lag behind the herd and become vulnerable to such a coordinated attack, however a
health adult sauropod accompanied by other healthy adult individuals would likely have been all but
immune to predation.
--
Dann Pigdon
On Mon, Jul 1st, 2019 at 5:02 PM, Poekilopleuron <dinosaurtom2015@seznam.cz> wrote:
>
> Yes, that sounds reasonable. But what if T. rex was just too hungry to wait
> any longer? Perhaps its mighty jaws could speed that process up a little.
> After all, 50+ tonne alamosaurs werenÃÂt agile enough to avoid a well-placed
> bite? Tom
>> If I was a tyrannosaur, I'd follow the herd around until something else
>> brought an adult down for me (disease,
>> injury, old age, etc). Such an event would have been the land-based
>> equivalent of a whale fall.
>>
>> --
>> Dann Pigdon