Re: [dinosaur] Fwd: Re: T. rex hunting Alamosaurus

[John Bois <mjohn.bois@gmail.com>]

We don't know how the sauropods managed their reproductive effort.ÂStrong arguments benefit both sides: did they lay and leave, like sea turtles; or, did they at least guard their nests like gators?

I think that if you come from stockÂwho apply parental advantage to their offspring, and that your offspring are delectable to many predators, that you also would want to intervene in that direction. Certainly, your qualms are valid. Just as a thought experiment, let us say that they _did_ guard their nests, how could they do that without either starving or destroying the surrounding habitat.

Penguin model: send off your parental partner to feed while you guard. When your partner returns, you go off and your significant other guards your babies.

Emu model:Âstore energy and water and go into extended, low-energy mode. Don't eat for weeks at a time. Pee crystalized uric acid to conserve your water!

Cicada model:Âdon't reproduce every year. This will give the producers time to recover and trick your predators.

The problem for you as a sauropod, is that your eggs represent a concentrated resource to your predators. If you are colonial (check), you return to the same nest sites (check), and you cannot hide or lay remotely (check, check), you are in a bind. When your babies hatch, they can disburse, hide, etc. and enjoy some relative security.

Re predation on adults: I agree with Dr. Habib on this. Perhaps ostriches are a good model...predation on adults is rare, predation on eggs and chicks is excessive. Suffice it to say that the majority of an organisms life is spent in adulthood. This then is the period where defense against predators should be strongest. Speed for ostriches, a mean kick for zebras, communal defense for water buffalo (e.g., Battle at Serengeti), stealth for squirrels, whatever it is, no doubt sauropodsÂwere likely able to defend themselvesÂ(with exceptions of course).

On Mon, Jul 1, 2019 at 11:55 PM Gregory Paul <gsp1954@aol.com> wrote:

Sauropods nests are irregularly constructed rather than well ordered like those that were tended to. The eggs would have taken months to hatch and the titanic adult sauropods would have denuded the surrounding landscape so they could not stick around. All trackways of wee baby sauropods show them moving on their own, sometimes in pods, never with big grownups, so there was no post nestling connection with the parents. Makes sense since juveniles massing a few kilograms could not keep up with 10+ t adults and would be trampled. Smallest juvenile trackways along with adults are bigger than cattle. So the herds were not like those of mammals with parents caring for their own young, they were juveniles who after living separate lives from grownups when became large enough to keep up and not be trampled tagging along with stranger adults who did not care about having juveniles in their company.Â

GSPaul

-----Original Message-----
From: John Bois <mjohn.bois@gmail.com>
To: Gregory Paul <gsp1954@aol.com>
Cc: dannj <dannj@alphalink.com.au>; dinosaur-l <dinosaur-l@usc.edu>
Sent: Mon, Jul 1, 2019 9:47 pm
Subject: Re: [dinosaur] Fwd: Re: T. rex hunting Alamosaurus

Gregory Paul said: "The idea that adult sauropods protected juveniles is extremely dubious because almost certainly the nests were abandoned upon being deposited,"

What is the evidence for your "almost certainly" claim?

On Mon, Jul 1, 2019 at 8:23 PM Gregory Paul <gsp1954@aol.com> wrote:

A lot of this discussion is iffy. Large predators do attack large healthy adult prey fairly often. We know that Tyrannosaurus attacked an adult Triceratops that was healthy enough to survive the attack as documented by Happ in the Tyrannosaurus rex anniv symposium volume. 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. The idea that adult sauropods protected juveniles is extremely dubious because almost certainly the nests were abandoned upon being deposited, probably one tonne+ juvies hooked up with adults for the passive protection of being with adults -- note we never find wee post hatchling trackways along with adults, they would have been accidentally stomped upon the indifferent adults they could not keep up with anyway.Â

Whether the specific species T. rex lived with Alamosaurus has not been documented, although the genus probably did.Â

-----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