Cynthia,
>>I assumed that all pigs would have the same number of teats!  By how much
would the number vary?  Is this true for other animals as well?  Were
the
extra teats like ancillary nipples on human moms, an unusual occurance,
or
are they a regular variance?<<

From what I recall (and this was 15 years ago that I worked with pigs,
well the animal variety anyway) not all pigs have the same number of
teats. Some breeds are noted for larger litters (around 12-14 piglets)
while other breeds were smaller (8-10 piglets). The smaller litter
breeds gaimed weight better and were often crossed with larger litter
breeds to get a good sized litter that gained well. The teats were
placed where one would expect them to be, but it seemed that the further
toward the rear of the pig, the less productive they were. The last pair
of teats teats looked more like token teats, rather than functional
ones. This was a common occurence. Not sure about other animals.

Maybe goats and sheep have 2 teats because multiple births are fairly
common after the first birth. Will ask people who know (from my life
before children, but was it really a life?)

Donna Hansen
Burnaby, BC where there aren't too many calls for animal science grads