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archive searching restored and more on "packs"



First off, I'm sure everyone will be thrilled to hear that a new
search engine has been installed for the dinosaur list archives.  It's
a little bit more functional than the previous incarnation.  I tried
it briefly and did find the exact post I was looking for.  Have fun
with it.  Don't thank *me*, though, since I had nothing to do with it.
The Cleveland Museum of Natural History provides the archives for us
out of their own good graces, and I'm not involved in their
maintenance.  The person currently maintaining CMNH's systems is
Stephen Sileo.  He's the guy who looked into a few search engines and
chose one that will hopefully work well for us.

In other news, Nathan Myhrvold recently wrote about pack hunting in
contemporary animals.  While the overall point of his message appears
to be one I'd go along with as a scientist with a vague familiarity
with some of the relevant literature, I think he has misrepresented
some of the views within the field.  In part I think that is because
he didn't heed part of his own advice:

> Bonnan is absolutely right that definitions are essential to this
> debate.

One of the terms that must be adequately defined is one that Nathan
not only used, but actually shouted at us: "COST".  Reading between
his lines, it appears to me that the cost to which Nathan referred was
an opportunity cost.  That is, in some studies it appears that lions
hunting alone or in pairs may be able to eat more meat per lion per
day than they are when hunting in larger groups (I'd mentioned this
before on the list:

http://www.cmnh.org/fun/dinosaur-archive/1999Apr/msg00700.html

but as I indicated at the time, it's not necessarily true that this is
the case in general for lions or whether it depends upon a variety of
factors extrinsic to the lions themselves).  Anyhoo, the concept of an
opportunity cost is an economic one, and in this context a biologist
is more likely to define a cost as an expenditure of energy or a
heightened risk.  Nathan's discussion did not include any references
to these sorts of costs, but some studies (at least for cape hunting
dogs) have suggested that these real costs are lower for animals
hunting in large groups than they are for animals hunting alone or in
pairs.  As such, Nathan's opportunity cost is irrelevant.  A lion may
get less meat when hunting in a pack with four individuals than it
would if it hunted alone, but if it spent much less energy locating,
pursuing and subduing the animals on which it fed then the *net*
benefit (the rate of energy gained - the rate of energy expended) may
be higher for larger group sizes.  Nathan appears to have focused only
on the rate of energy gained (or in terms of the statistics that he
actually quoted, probability of a successful attack given that an
attack occurred), which is not enough of the whole picture to
determine whether or not there is a "COST" associated with hunting in
large packs.

Bottom line: as Nathan and Matt (and others) have pointed out, it's
difficult to understand what's going on with pack hunting in extant
animals.  I'll add that currently there's not a lot of point to
speculating about it in extinct ones, but I don't expect that to
prevent people from continuing threads like this here...

--
Mickey Rowe     (mrowe@indiana.edu)