Re: About those Piranha Bugs - and more vileness

----- Original Message -----
From: K.H.Ranitzsch <KH.Ranitzsch@t-online.de>
To: <gzg-l@csua.berkeley.edu>
Sent: Saturday, January 12, 2002 8:00 AM
Subject: Re: About those Piranha Bugs - and more vileness

>
> ----- Original Message -----
> From: "Robin Paul" <Robin.Paul@tesco.net>
> > A possibility is that the mounds are mud structures in which the PBs
rest-
> > only a migrating herd of Buffaloids can break the mounds, and that
> triggers
> > the feeding behaviour of the PBs. The PBs therefore needn't be
> territorial,
> > in the sense of defending a territory- the victims have just acted
like
> food
> > at feeding time.
>
> Over evolutionary times, the herd animals would learnt or evolved to
avoid
> damaging the mounds, unless the toll was *very* low.
>
> Greetings
> Karl Heinz

The toll can be lowered in several ways-
Perhaps the herd is so huge that the PBs eat their fill rapidly and
ignore
the rest of the herd.
Perhaps the herd move very fast, and the PBs are like cookie-cutter
sharks,
taking tiny bites from each Buffaloid but not doing any lasting harm. 
If
humans are dim enough to just stand there in small numbers, they can
hardly
blame the PBs for just eating them :-).
Perhaps the cost of NOT risking the PBs is vastly more than the
alternative-
compare the wildebeeste herds which _have to_ cross the river regardless
of
crocs, or starve to death.

The PBs may be deadly to individual herd animals, but comparitively
insignificant to the herd, so there would be little selection pressure
from
PBs on Buffaloids.

Rob Paul