What about cows, horses, sheep, deer, goats, etc, that have 2 or 4 teats
and usually only one or 2 young?  What prompts those babies to switch
sides?  I've always figured it was the baby's desire for more milk *or* the
mom moving to another patch of grass.

Diane Wiessinger, MS, IBCLC, LLLL, learning animal husbandry thru lactnet
in  Ithaca, NY