Re: Phorusrhacids killing large mammals in National Geographic Channel

[Augusto Haro <augustoharo@gmail.com>]

> I'm not too well versed in biomechanics, but any chance that the beak
> could have been adapted (or at least used) for slipping in between
> vertebrae and snapping the spine along the neck or back?

May be, my guess was that the tips would penetrate between the ribs of
a German Shepherd-sized prey, I suppose it can also function against
the cervicals of a horse- or tapir-sized prey. After seeing this
picture I think a single bite of this beast to the breast may kill any
human-sized mammal, and perhaps larger:
http://www.rom.on.ca/collections/curators/graphics/seymour03.jpg.

> Could prey have been knocked off-balance with the feet (or even the
> head) and then held down or otherwise finished with the beak? Or
> perhaps the upper beak's hook was used to drag prey off its feet and
> then kicked/held down for a bite/bitten.

It seems weid to me that a tall bipedal bird can make a shorter and
stockier quadrupedal mammal its same size (say, a boar-sized one) to
fall with kicks (although perhaps I underestimate the bird or
overestimate the mammal resistance).

> I guess the lack of (IIRC) any marsupial carnivores bigger than
> leopard-sized on a continent with plenty of big game strikes me as
> reason to suspect at least *some* phorusrhacids were real threats to
> larger herbivores, as well as dominant at kill sites.

May be that they were dominant (the idea of the kill site antagonisms
reminds me of the ugly image of the Titanis killing Smilodon gracilis
by using a woodpecker's technique), because the bird is tall and may
have screamed as many birds intimidating the smaller carnivores. In
addition, if it can kill a human-sized mammal, the same can go to a
leopard-sized animal. However, a leopard-sized carnivore may have as
well been dangerous for the relatively lightly built bird.

However, I am not sure about the fact that big game would be not used
as a resource without the intervention of the birds, after all, by the
Pliocene you also have saber-toothed marsupials, which even if
leopard-sized, would pose threat to tapir/horse-sized mammals.