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Re: Behaviour Bias



Judy Molnar wrote:

>What data [for dinosaur behaviour] is that?  Has dinosaur >intelligence
fossilized recently?

Yes, as endocranial casts (likely as close as well ever get to seeing a
dinosaurian brain).  

>Just because the brain casts are not the same shape or size >as similar
mammals doesn't rule out complex behavior. 

Endocranial casts allow us to determine the ratio of brain weight to body
mass, which is very, very important in determining "how intelligent" an
animal may have been (or be). Good endocranial casts also allow us to
determine precisely how that intelligence might have manifested itself, by
demonstrating evidence of brain morphology (i.e., the size of the optic
lobes, frontal lobes, etc.). 

>Cephalopods (octopus) do quite well in the behavior >department with very
tiny brains!

Bad example. Actually, octopus brains are rather large (the largest of any
non-vertebrate), both as regards absolute size and size relative to body
weight. Furthermore, despite there admittedly impressive intelligence, they
do not tend to behave like mammals and have no direct bearing on this
discussion.

>But I think this is a normal "let's swing the pendulum way >over in the
other direction to compensate for that silly old >error" response. Pendulums
do swing back and find a nice >middle ground eventually.

This is not exactly a prescription for good palaeontology (or any other
science, ftm). See Thomas S. Kuhn's THE STRUCTURE OF SCIENTIFIC REVOLUTIONS
(1962, Univ. of Chicago Press).

>I don't think this [bias] can be helped, just noted that it exists >and we
need to be aware of it.  

If it can be recognised, if we are aware of it, it can be helped. 

>But if mammals have taken over most, if not all, the >ecological niches
vacated by dinosaurs, then I see nothing >wrong with using mammals as a
model.

Because we can only reason from the evidence at hand. With dinosaurs, that
evidence is limited to fossils, which means we may only study behaviour
indirectly. While we can often draw broad ecological parallels between
extinct and extant organisms based on fossil evidence, it is only very rarely
that we can soundly make more specific inferences (those rare exceptions do
exist and I'm not trying to discount them). 

It's safe to say that both _Allosaurus_ and _Felis leo_ are relatively large
(with regard to their respective prey species) terrestrial carnivores,
preying primarily on terrestrial herbivores. After that, things begin to get
fuzzy, and the more specific our comparisons, the fuzzier they become (for
instance, if we were to say that allosaurs, like lions, are ambush predators,
or that, like lions, allosaurs must have hunted in cooperative "packs").  

>But why limit yourself?

Because I am a scientist and that's how I was taught to do science.

>My impression was that their WAS evidence for pack hunting >in the fossils
-- e.g., finding several Deinonynchus with a >Tenontosaurus (SP?) in such a
manner to strongly suggest >they died trying to kill it. 

I know of no direct evidence of _Deinonychus_ "packs" preying on
_Tenontosaurus_, but this is not my area of specialty, and I may have missed
something. I am aware of the association of the two taxa in one of the YPM
_Deinonychus_ quarries, but I've read nothing that would demonstrate that,
even if the _Deinonychus_ did feed on those particular remains, that they
were responsible for the animals death, or that they in any way cooperated in
the kill. If we are going to accept that a pack of _Deinonychus_ brought down
a tenontosaur, first we're going to have to rule out reasonable alternatives,
such as scavenging and incidental association.

>how exactly do you go about testing the pack hypothesis if
>the behavior won't fossilize (other than in the way described >above)?

How can we test a pack hypothesis? My guess is that it would be extremely
difficult, if not impossible, to ever conclusively demonstrate that any
extinct theropod species hunted in "packs." There are too many other equally
plausible explanations. For example,  a little earlier, someone brought up
group foraging among extant predatory birds (I can't recall the specific form
involved). How, on the basis of a fossil association of the mixed remains of
multiple individuals of _Deinonychus_ and a single _Tenontosaurus_ (this is a
hypothetical example, as I know of no such actual association), do we
distinguish between these two possibilities? Or rule out the possibility of
the ornithopod having expired from disease and then being discovered by the
theropods? Or that the _Tenontosaurus_ was killed by a larger theropod that
ate its fill and left the scene to scavengers (and while I don't think
_Deinonychus_ *looks* like a scavenger, it may well have scavenged
opportunistically). 

Sorry for going on about this at such length. But an awful lot of tenuous
behavioural modeling is being treated, increasingly, as fact (especially in
popular and semi-technical works) instead of as the merely intriquing (and
often untestable) ideas that they are.

Caitlin R. Kiernan