Re: Phorusrhacids killing large mammals in National Geographic Channel

[Augusto Haro <augustoharo@gmail.com>]

You may be right, Graydon. Beating prey against the soil or branch
where the predatory bird sits is common in many other predatory birds
without enlarged talons, as kingfishers, some South American tyrants
(Tyrannidae, not talking about Pinochet or some many others),
seriemas, and secretary birds. They may replace the lack of killing
weaponry this way. I forgot, Dann, there seem to be "peckers" which
use slightly curved beaks to peck on prey as you hypothesize: the
hornbills (Bucerotidae), which seem to be turkey-sized and can kill
rabbits this way according to documentaries (I suppose not-so-large
rabbits). I suppose a Phorusrhacos, weighting approximately 130 kg.,
may have little proble in picking up a German Shepherd-sized mammal
(some 30 kg.) more than a meter from the ground and then hit it head
first against the soil. After some repetitions of this the prey would
be left at least unconscious. Perhaps if pursuing such mammal, they
would grab the hind quarters first and then make the first blow
against the soil with the head, for putting the prey unconscious
before it can even try to bite (these mammals may have tried to bite,
as many rodents do when cornered).

I was thinking on the killing devices of phorusrhacids and it seems to
me that the tip of the upper jaw is much more prominent than in other
carnivorous birds I know. Also, differing from Falconiformes and
Strigiformes, the lower jaw also presents a tip which would have
penetrated into the prey while biting. Considering these processes
would be longer with the horny cover, when these birds bite, the prey
would likely be severely stabbed, especially with the upper process,
which is longer. Such a stabbing bite may even be severe if delivered
to the thorax of an animal the size of a human being. The tall beak
would better resist those biting (orthal) forces. I think that if the
bird performed a number of fast bites, any mammal the size of a German
Shepherd would suffer too many perforations and likely die soon. I
imagine terrestrial predatory birds which hunt without enlarged talons
tend to be quite tenacious against prey, for they sometimes have to
attack venomous snakes. I suppose the phorusrhacid may have to kill a
medium-sized mammal with some number of these bites, at the time it is
trying to avoid the attempts of the mammal to bite back (somewhat
similar to the duels of smaller seriemas against venomous snakes).

2009/7/22 Graydon <oak@uniserve.com>:
> On Tue, Jul 21, 2009 at 03:21:25PM -0300, Augusto Haro scripsit:
>> Unless phorusrhacids shake their heads to the sides like crocs and
>> dogs, then they may easily kill animals half their size, but I do not
>> know of birds which do so.
>
> Herons have been observed drowning rabbits; roadrunners have been
> observed beating snakes on rocks.
>
> The idea of doing the dog-style shake is not going to fit with the
> morphology but something analogous seems plausible based on extant
> examples.
>
> -- Graydon
>