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Re: Phorusrhacids killing large mammals in National Geographic Channel

> Well, perhaps you are right and I should stop this argumentation
> regardless of we do not agreeing in some points. It went somewhat off
> the killing method of phorusrhacids anyway.

Yes, yes it did. ;)

And I don't think we really "disagree" *too* much - we just have
different perspectives on things that have yet to be quantified in any
useful way. So it's all good.

Let's all just agree that the idea of huge avian dinosaurs killing big
mammals is cool. :o
"I've got no numbers, of course, but the impression I get is that size
and aggression correlate in herbivores, with larger ones being more
likely to be aggressive and attacking would-be predators. Perhaps the
reason the only thing in that size range is cantankerous is that any
herbivore that gets that large grows cranky."

Nah, bigger herbivores can *afford* to be cranky. So can a few
specialized small ones, but not most.

Gazelles? Small and frail compared to most predators, can't compete in
terms of mass or power; much safer to flee than to resist, since
they're not going to be stilletoing multiple lions with their horns
anytime soon. Unless they're ninja gazelles.

Rhinos? The smallest black rhinos have about three times the mass of
the largest lions; most other rhinos are even bigger. Lions could
probably take an adult one down if they were desperate, but not
without serious risk of injury or death to multiple members, because
rhinos can trample and gore their foes in a way no gazelle is
physically capable of matching.

Porcupines? Smaller and weaker than any gazelle, but by comparison
they're armed to the teeth. They don't need to flee, so they can't be
considered "flighty" or "not bold," but they have more of a passive
defense than a vigorous offense. There's more than one way to stick a

So I would claim, again, that at the very least, aggression has to be
backed up by ability within a selective context. If you're big and
strong enough, quick and pointy enough, or slow but bristly enough to
protect yourself through resistance, then that can be selected for. If
turning and taking on your attackers routinely ends with you
contributing to their annual caloric intake, you should hope your
species gets selected for a strategy that actually works.