Re: Herbivore protection

[Matt Fraser <mattf+@pitt.edu>]

On Thu, 5 Jun 1997, John Bois wrote:

> I don't know of any reason why a wildebeest couldn't have many small
> babies rather than one big one.  I would be really interested to find out
> though if there is such a physiological constraint.  I'll post this on
> sci.bio.evolution, if you don't mind.  In the meantime, ponder a
> K-strategist elephant--eighteen tiny elephants--does it compute?  

Keep in mind that: 1) Mammals have to nurse their young.  Eighteen tiny
elephants will grow to "suck the life" out of a mother, assuming that they
are all weaned at the same size that infant elephants are currently; 
2) Many of these animals have precocious, rather than altricial, young.
This is a survival necessity.  The young must be ready to bolt in the face
of predation in fairly short order.  This means a relatively high degree
of prenatal development, particularly neural and skeletal development.
One would not want this degree of skeletal development to occur in a "too
small" animal, as the normal course of events would lead to a "too small"
adult.  The neural development aspect is important in this regard as
well.  Eyes open at birth means that they can see where they are running
and from whom. Mammals that "nest" have litters, and their young are
altricial (totally dependent, underdeveloped, often eyes closed at birth
reflecting underdeveloped nervous systems); and 3) The limit
physiologically to the mother as far as how many infants she can carry to
the properly developed state based on her ability to maintain that many to
a stage that they are developed enough for the animal's "life style".
Eighteen tiny elephants would be severely premature, and if could live,
would be more like rat pups.  Elephants would need to nest.  Doesn't fit
the roam and forage life style.

Dinos, on the other hand, because of egg laying, need only protect the
nest and young after they are born. The large eggs can be passed as soft
bodies, and harden later (maybe).  Little physiological investment
relative to a mammalian mom (although I am sure there are extreme
circumstances, like the hornbill and the penguin - interestingly they have
few young!).

Just some thoughts,

Matt

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Matt Fraser
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