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Re: DINOSAUR BEHAVIOR



> Jay, I certainly defend your right to enjoy JURASSIC PARK, but your idea
> that any of the behaviors depicted in that movie are "plausible" needs to
> be questioned.

  Certainly!

> Dinosaurs were *never* capable of behaving like lions.

  Field ethological expeditions to the Cretaceous being infrequent, we
are perhaps all most wisely advised to let that one lie.  However, I
never said I was wise, now, did I?  Therefore...

> No bird or crocodilian species alive today - the groups that
> phylogenetically bracket dinosaurs -- hunts cooperatively.
> Only mammals do.

  Harris' Hawks hunt cooperatively, in the rather complex sense of
taking turns harassing prey (Bednarz, J. C. 1988. "Cooperative hunting
in Harris' Hawks (_Parabuteo_unicinctus_)", _Science_239:_ 1525-1527,
cited in Frank B. Gill, _Ornithology_, 2nd ed., W. H. Freeman, 1994,
p. 339).  Other complex social behavior, in family groups that are
reminiscent of canid packs, is widely reported in corvids.  Less
complex behavior, including mobbing, smoking (a response to predators,
not to nicotine), flocking, and migrating in formation, is of course
well-known, perhaps in a majority of avian species.  There are also a
number of citations of spontaneous avian tool use (that is, unprompted
and untrained), and the ability of some caged birds -- notably parrots
-- to learn to maniuplate locks and latches is well-known.

  To the extent that such behaviors are the subject of discussion, a
sophist who believes that birds are a derived group of theropods might
argue that we have now demonstrated by direct observation that
dinosaurs not only *are* capable of behaving like lions, but in fact
do so regularly.

> Therefore, assigning mammalian traits to dinosaurs is a practice that is
> questionable at best, since there is no relation between the two.

  Nor is it necessary, since these traits are found in much more 
closely-related taxa. 

  I must admit to ignorance on a relevant matter: Is there any
substantial ethology on crocodilians or on any of the big lizards?  I
have certainly seen video footage of groups of Komodo dragons feeding,
and I have seen crocodilians in close proximity to one another
(alligators).  At least modest social interaction seems therefore
likely; does anyone know how complicated it gets?  The amount of field
study that has been done of large charismatic mammalian species makes
it particularly tempting to conclude for other species, that absence
of evidence of a particular behavior is evidence of absence; I suggest
that a better conclusion may be that for the most part, no one knows.

> Furthermore, even in mammalian groups, only a figurative handful of
> predators hunts cooperatively.

  I did not suggest that all predatory dinosaurs hunted cooperatively.

> ...the bird or crocodilian brain (and thus through inference the
> dinosaur brain) is incapable of the higher functions necessary to
> perform [the task of cooperative hunting].

  On the bird end, that's refuted by direct observation, cited above.

> Regarding the intelligence of some of the smaller theropods, studies
> of fossilized braincases give good indication as to the size and
> complexity of their brains and [comparison to ostriches and emus]...

  If they are as smart as parrots, padlock your door and hide the key.

> Some modern birds -- raptors, psittaciformes -- are *much* more
> intelligent than any theropod ever was.

  Conjecture.  And to some of us, raptors and psittaciformes *are*
theropods, though I know what you meant.

> Male and female raptors are known to circle together searching for
> prey, but even they do not both attack an animal simultaneously to
> kill it and then share the spoils.

  The Bednarz citation describes exactly the latter behaviors, in
family groups.

> Bay-winged hawks ...

  I've not heard of them.  Citation?  Further description?  Or is
this an alternative name for the Harris'?

> It is also debatable whether aerial hunters are good analogues for
> behavior patterns of strictly terrestrial predators.

  I agree, though the behavior seems comparably complicated.

> the only models we *can* use to even *speculate* about their
> behavior are those that are observable in the modern world

  I agree, though we seem to disagree on the scope and perhaps the
interpretation of what is observed.  I will admit to awarding low
weight to comparative anatomical studies of gross crainal size and
features; encephalization always sounded to me overmuch like
phrenology with a Ph.D., and seemed unlikely to predict, for example,
such tool use as has been reported in corvids, who have a brain 
the size of your thumb or smaller. 

                                                --  Jay Freeman