Re: read and learn

[Jonathon Woolf <jwoolf@erinet.com>]

Colette H. Adams wrote:

> Here's a can of worms I actually would like to open.  On many occasions I
> have heard it suggested that ceratopsians would have turned on their
> attackers and used their horns for defense rather than flee.  Forgive me,
> both those who suggest such a thing do not understand natural selection.
> Let's imagine we have a herd of ceratopsians.  A tyrannosaur shows up.
> Some of the ceratopsians have the "run like hell" gene.  Some of them have
> the "turn and defend" gene.  Now who do you think will be passing their
> genes to the next generation?  Natural selection will ALWAYS favor "run
> like hell."  If the ceratopsian cannot flee, then of course it will defend
> itself however it can.  But it will always go for the flight option first.
> Triceratops horridus did only one thing when it saw, heard, or smelled
> Tyrannosaurus rex.  It ran like hell.

That makes sense in concept, but alas, nature doesn't always act sensibly.
Natural selection does not _always_ favor flight vs. fight in prey.  Selection
favors any defense tactic that works.  If fighting works, fighting is selected
for.  If running works, that's selected for.  Evidence from observation of 
modern
animals suggests that both are valid defenses, depending on the terrain and on 
the
animal using them.  For example:

Zebra are fast and live mostly in open and semi-open country.  Zebra have no
effective fighting weapons against predators.  Therefore, zebra run when
attacked.  The same is true for pronghorn antelope and many kinds of gazelles.  
No
weapons, open country, so they run. However, other African animals like water
buffalo have the size, strength, and defensive weaponry to fight successfully, 
so
fight they do, and sometimes they win.

Or switch to a different animal in a different environment, say wolves vs. moose
on Isle Royale.  L. David Mech spent a couple of years watching predator-prey
relationships on Isle Royale.  Among other things, he watched a number of wolf 
vs.
moose encounters.

"Out of the 160 moose that Mech saw from the air and judged to be within range 
of
hunting wolves:
        29 were ignored,
        11 discovered the wolves first and eluded detection,
        24 refused to run when confronted and were left alone.

Of the 96 that ran:
        43 got away immediately,
        34 were surrounded but not harmed,
        12 made successful defensive stands,
        7 were attacked,
        6 were killed,
        1 was wounded and abandoned."
-- from OF WOLVES AND MEN, Barry Holstun Lopez, p. 57

Mech and Jim Brandenburg saw the same thing in their observations of the famous
Ellesmere Island pack when those wolves hunted musk-oxen groups.  As long as the
oxen stood and held their defensive formation, the wolves could not make a
successful attack.  Only when the group was spooked into running could the 
wolves
close and make a kill.  So for moose and musk-ox, two large and powerful animals
with effective antipredator weapons, fighting is at least as good a solution as
running is.

Any prey animal that confronts a predator is saying basically, "I'm ready and
willing to fight you for my life."  In that situation, it's not in the
_predator's_  interest to force a fight, because in any fight there's a risk of
injury to both parties.  A lot of wolves have died from an antler-swipe or a 
kick
from a moose before the moose finally went down.  There are always other prey
animals around, so there's always an easier meal to be found.  Why fight when 
you
don't have to?  So fighting is an effective defense for a prey animal that has 
the
tools to fight, because predators have learned it's not a good idea to fight a
willing foe.  Better to just walk away and live to hunt another day.

-- JSW