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Re: Raptors climbing trees?
On Thu, Apr 03, 2008 at 04:50:41PM -0400, email@example.com
>> Until I saw the YouTube bit with bunches of goats in a huge tree, I
>> wouldn't have been arguing that goats were tree climbers!
> That of course is my point exactly; goats are NOT tree climbers. Oh
> sure, they can (and do), but at this point the behavior plays no
> significant roll in their evolutionary success.
But goats _do_ have adaptations for climbing; these started in
mountains, but they apply to trees. (the ability to grip with the
cloven hoof, narrow gauge stance, balance, and probably some others.)
> If that were to somehow change in the future then whatever the
> selective process is will probably encourage specialization to their
> incipient arboreality that would be evident in their morphology.
How do you tell the adaptation from the exaption? Especially initially?
My take on this is that goats are good enough at climbing trees, by
borrowing adaptations for climbing rocks, that they get significant
benefit from it -- our milk goat could get apples out of an apple tree
by climbing it that horses couldn't reach, for example -- that it's not
likely to go away even in a complete absence of rocks. But it's also
not likely to become a significant specialization, because being _more_
specialized would start to be a disadvantage in other modes of life.
Being primarily arborial, fossorial, or scansorial is different from
some useful amount of ability in those areas. I don't think it's
possible to tell exactly what that useful amount was in a fossil
creature, but there's rarely a single mode of life through the whole
period of a creature's lifespan. Bears, for example, or pigs, or just
about any passerine bird there is, have multiple foraging strategies
that apply at different times and life stages.
Especially in the case of something like a dromaeosaur where they're
clearly specialized for something but we can't tell precisely what, I
think there's a fair bit of value in trying to set limits on the shape
of the ecological space they lived in, because that might eventually
give some sufficient hint about what they were specialized for...