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Re: Gangs, packs, etc.



Nathan, 
I find your statistics interesting. 

Were there any statistics on these same lions on how frequently/often
the same lion would kill? a particular two lions would kill? or a
particular pride would kill?  I suspect a group would hunt sooner after
a succesful kill than an individual would as the individuals would be
hungrier.  Thus the time that each indidual spends hunting increases
while in a group.

Were there statistics with these same lions on how often a single lion
succesfully comandeered a carcass from another groups' kill as opposed
to an individual succesfully doing the same thing?  I suspect again the
group would be more succesful at comandeering/bullying possesion of a
kill than an individual would.  The advantage on the African savannah is
obviously that a group of carnivores will protect the kill against other
groups of carnivores better than an individual can, and be better at
bullying as well.

As has been mentioned, both the African predators and wolves are made up
of family groups. Both younger and older individuals make up the larger
groups whereas the smaller groups are usually littermates. 

I ramble on further....

-Wolves don't compete with other groups of hunting carnivores like
lions, baboons, hyenas, or african hunting dogs have to, and yet they
still hunt in groups.  There must be an advantage outside outside of
bullying and protection.  I suggest that hunting in groups is a
succesful strategy as it has the young making succesful kills as often
as the more experienced adults sooner than they would on their own. 

-I suspect the individuals in a family group will be able to hunt longer
and be older than an animal that hunts totally on it's own, and able to
assist in a kill with minor injuries that would hamper an animal totally
dependant on itself for it's survival.

-Both of which contributes to the success of the related genetic
inheritance of those family groups.  These animals hang out together not
to be more succesful than nongroups, but to be succesful LONGER as
individuals than nongroups, and as succesful as competitive other
species that group.

All we know about dinosaurs is that some grouped.   We don't know the
relatedness of a group (but probably related), nor the ages of the
individuals in the group (unknown), nor even how long the individuals
could live to know if living in a group would improve survival over not
in a group.  

If dinosaurs continued to grow until they died, did they become aged and
wizened?   Would old age creep in on a dinosaur at the same point in
growth in all individuals of the same species or did the metabolism
change with diet or health?   Would a hatchling Allosaur or T rex under
a meter in length be recognised by an adult of it's species as the same
species, much less as a relative?

I can think of more reasons to wonder about dinosaur behavior and
metabolism from this 'association' of one species than I can think of
answers.

-Betty Cunningham

Nathan Myhrvold wrote:
> 
> Bonnan gives an excellent summary of the situtaion. I basically agree with
> him, but differ on a couple key points.
> 
> The "mammilian pack hunting" model is the dominant popular view (i.e.
> Discovery Channel et. al.).  Older scientific work also supports the notion
> of close cooperation in mammilian carnivores like wolves, lions etc.
> However, more recent field studies have largely discredited this view.
> There is no hard evidence that a deep level of cooperation exists.
> 
> The most important such study was Schaller's work on lions in the Serengeti.
> He witnessed 523 hunting events and recorded the statistics of success for
> various numbers of lions.  Here is the results of hunting success for all
> kinds of prey:
> 
> 1 lion  15%
> 2 lions 29%
> 3 lions 27%
> 4-5 lions 32%
> 6 or more lions 33%
> 
> (from table 59, The Serengeti Lion)
> 
> So, two lions are basically just as effective hunting together as they would
> be if they hunted separately (actually, slightly less successful, but that
> is within experimental error).  There is NO difference in effectiveness due
> to hunting "cooperatively".  They get the SAME results they would get if
> hunting alone - they just happen to do it together.
> 
> After two lions, the story get worse.  Three lions are about as effect as
> two, and WAY less effective than if they split up.  Adding additional lions
> does not help. The statistics above are for all prey, but Schaller's tables
> breaks it down by each prey animal and the same result applies.
> 
> Since Schaller's study (1967) numerous field biologists have documented this
> with increasing accuracy for lions and (particularly work by Craig Packer)
> and in wolves (Thurber and Peterson, J Mammology 74(4):879-889, 1993) and
> other group hunting carnivores.  The same conclusion holds - "packs" have NO
> benefit, and usually a large COST when compared with the same number of
> animals hunting alone.
> 
> You might think, OK, that is hunting success, but what about number of Kg of
> meat, or reduction in variance of hunting success, or size of prey.   Maybe
> they get the same percentages, but they can kill larger prey, or hunt more
> often, or more reliably...
> 
> All of these measures, and many more, have been tried and failed.  There is
> no detectable advantage to so called cooperative hunting.   The best current
> theories of social hunting (particularly Packer's work s see Heinsohn &
> Packer, Science 269:1260-2, 1995) are not based on hunting success at all,
> but rather other social interactions (holding a territory, reproduction).
> 
> So, if you believe that "pack hunting" mammals have deep cooperation, you
> must explain how it is that they get ZERO benefit from it.  In fact, they
> frequently get very high COST compared to splitting up and hunting
> individually.  If it does not have any measurable impact in terms of
> success, is it really cooperative?
> 
> The same field biologists who gather these statistics also have described
> hunting in detail.  Their reports are consistent with the conclusion - there
> isn't a lot of deep cooperation.  For every case where it appears that a
> lion flushes prey into the waiting grasp of a pack member, there is a case
> where the lion flushes prey the wrong way.  We don't tend to see that flim
> clip on the Discovery Channel.  By counting only the sucesses, we make them
> look very good.
> 
> Detailed field reports are consistent with lions, wolves and other group
> living mammilian carnivores being what Bonnan calles "gang hunting" - i.e.
> pack members hunt together, and rush to grab the same prey.  Selective
> reporting and anthropomorphism lead us to conclude that great intellegence
> is involved.
> 
> Of course, these animals ARE individually quite intelligent, and they are
> highly social with a rich set of social behaviors, some of which are
> expressed during hunts. They are excellent hunters, and do have the ability
> to anticipate their prey in hunting (there is good evidence of this).
> 
> So, I am not suggesting that lions and wolves are dumb, or that they are
> dumb hunters.  However, available evindence suggests that this intelligence
> is expressed invidually, and that they do not have deep levels of
> cooperation in hunting.
> 
> The implication is that high intelligence is required if you want to be a
> wolf or lion, but there is no indiciation that high intelligence is required
> to cooperate in hunting as well as a wolf or lion.  "Pack hunting" is NOT as
> effective as people think, and does not require high intelligence.
> 
> Lions and wolves are social creatures and hang out together when they hunt,
> just as they do when they sleep or do other functions.  When hunting
> together they probably are "gang" hunters - i.e. they each follow an
> individual strategy, with little or no input about what their companions are
> doing
> 
> There are MANY well know examples of simple, individual behaviors giving
> rise to apparent complex group behavior.  Schooling of fish, flocking of
> birds, and many other things have been shown to be due to this.
> 
> Note that I am not saying I have hard evidence that this is preciesly what
> lions and wolves do - that is a stronger statement.  However, the evidence
> is very consistent with this, and it is NOT consistent with deep levels of
> cooperation.
> 
> Gang hunting exists across a large swath of the animal kingdom, all the way
> down to army ants.  In fact, it is quite likely that ant hunting statistics
> would show that ants probably get far more benefit from their gang hunting
> than lions or wolves do from their pack hunting.
> 
> There are birds which "pack hunt" (again, most likely gang hunting), notably
> Harris' hawk.  Most predatory birds are solitary, or live in pairs, so
> broadly one can concude that are not group hunters.  However, there are many
> species of social living birds (albeit not raptors).
> 
> In conclusion:
> 
> -  Bonnan is absolutely right that definitions are essential to this debate.
> 
> -  Pack hunting by mammals is not supported by hard data.  If it exists, it
> does not effect hunting success, which is very hard to explain.  Most
> likely, so called cooperative pack hunting is really just gang hunting -
> simple piling on.
> 
> -  Theropods cannot be ruled out as gang hunters, on the basis of
> intelligence since gang hunting occurs in such a wide variety of animals.
> 
> -  In particular, pack hunting (which is probably gang hunting) does occur
> in some birds (although not in most predatory birds).  As a result, the
> extant phylogenetic bracket method cannot be used to rule out gang/pack
> hunting for theropods.
> 
> -  At the very least, the discussion above should make the point that it is
> suprisingly hand for field biologists to get hard data on how well LIVING
> animals cooperate in hunting.  Determining this with any scientific accuracy
> for extinct animals is far harder yet.
> 
> Nathan

-- 
Flying Goat Graphics
http://www.flyinggoat.com
(Society of Vertebrate Paleontology member)
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