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RE: Dino coloration and more...



Betty replied to my posting on coloration with a number of very good thoughts,
but I have a few replies, before moving on to other things:

>Wayne said:
>
>> Animals whose primary predators are colorblind (e.g., zebras) may
>> sport a camouflage scheme that's highly visible to color-sighted
>> animals (e.g., us).
>
>which does zebras no good when they're predated upon by us   
>color-perceptors.

Quite true. I was kind of leaving humans out of the system.

> the quagga (a striped zebra relative removed from existance by the Victorian
> era) is now extinct by being predated upon by color-perceptors that could see
> stripes from a closer distance just fine, than you.

My point exactly. Until color-sighted predators (Victorian Englishmen)
started trophy hunting, the quagga was doing OK.

>>         Highly visible animals occur in two situations: where the environment
>> is similarly colored (rain forest butterflies and birds), and where there is
>> no need of camouflage or stealth (skunks, poison frogs).
>
>umm-highly visible animals appear where their coloration helps them   
>survive. In brightly colored jungles, brightly colored mates are easier   
>to find.  And in any situtaion, nasty, poisonous animals are colored so   
>that the memory of eating ONE (or messing with as in the case of skunks)   
>of them helps the rest that are marked simiarily to survive.
>
>> It's interesting to note that very few predators have high-visibility color
>> schemes -- the coral snake is the first that comes to mind, and that's
>> defensive.
>
> I won't argue with you, but will mention wasps, spiders, and other   
>carnivorous insects that are brightly colored. And have other means of   
>defense other than looking colorful.

The colorful wasps etc. are examples of those I mentioned above, which have
no need of stealth. Like a coral snake or a skunk, a yellow-and-black wasp
says, "Don't even THINK of eating me!"

>>Finally, since flowering plants didn't show up until the Cretaceous, I'd   
>>expect most creatures to be more in the drab shades until then.
>
>     Plants don't have to be flowering to be brightly colored.  The fall   
>coloration of decidous trees makes a very nice place for the red bat and   
>the red fox to hide in and they're amongst the brightest colored of   
>mammals

Point well taken -- I wouldn't presume to argue. Please note, however, that
I was dealing in general thoughts on coloration, and most generalities have
exceptions.

On to flight, meganeura, and Steven Throop:

I saw an article in a recent science magazine -- unfortunately, I forget which
one, but I could find it if somebody really wants to know -- called, "Insects of
the Oxygeniferous." This dealt with the theory that Carboniferous insects grew
to such heroic sizes largely due to a much higher oxygen content than is found
in the current atmosphere. Presumably the Mesozoic atmosphere was closer
to ours than that of the Carboniferous, hence the decline of big bugs. That, and
the "hellatious" lift generated by a dragonfly-style wing system could easily
accomodate the evolution of meganeura.

And Steven Throop wrote of flying fish:

>The advantage of a fish's leap would seem marginal.  Being bigger, the
>pursuing fish would have more speed and stamina.  Probably the pursuer could
>pretty well keep up with the glide and estimate where the prey would splash
>down.

This makes a wild assumption: that the pursuing fish can watch the gliding
prey through the rippling surface (try it next time you're underwater!), and
completely misses the factor of surface drag. How fast is a flying fish's
glide? 10 MPH? 15? 20? (Aynbody know?) It clearly has to be above a 
stalling speed, and I doubt that the flying fish has evolved anything as 
sophisticated as an alula to delay stall. Now, how many marine predators
can maintain that kind of speed in water? Barracuda? Dolphins? Is the
prey even worth the energy it would cost? Surface drag in water is FAR
more than the minimal aerodynamic drag a flying fish would generate.
Ergo, a flying fish does effectively escape with a simple glide -- and they
would be extinct if it didn't work.

>...as far as I know, none has developed enough lift to turn.

Any pilot can tell you that turning doesn't require lift -- you can trade
altitude for a turn. The highly technical term is "banking".

And, finally, about the preserving of feather impressions vs. scale impressions:
Try a simple experiment: Mix up some plaster to any consistency you choose.
Get a dead bird and a dead lizard. Push them both into the surface and see
whose skin impressions remain. What you find is that feather impressions will
be "illegible" in any firm surface, where scale impressions will "print" nicely.
Feathers are simply softer, and the consistency has to be JUST RIGHT, or you
can't use it.

That's all for now.

Wayne Anderson