Sounds like its meant to be gross or funny, I'm going on a limb and say you never see any of them poo.
It is a common convention that, even though we know all the characters in pretty much every story in literary history (possibly excepting some aliens or spiritual creatures) would do that, it is never mentioned. Unless it is suitable to create some prophane atmosphere or somebody is to be murdered in the bathroom it is just never mentioned but taken for granted. No reason why LBT should be different.
The entire valley got pretty pissed off at Littlefoot in LBT 11.
Littlefoot had had an accident which deprived the others of some treesweets and he lied to shift the blame on the tinysaurs he did not know at that time... Big deal. He did not knowingly risk anybody's safety, he was not able to foresee the consequences of his actions. It was less serious than what I am thinking of.
You never see any of the youngsters come into physical confrontations with one another.
Littlefoot and Cera are fighting in the original and the fifth movie. Nobody gets ever really injured physically... and come to think of it this is something they could include. In spite of all they have gone through we never saw any of the characters worse off than loosing consciousness for a few seconds. Some more severe injury (no lasting damage intended of course) might be an interesting element in a story. One thing I have in mind in one story would have Petrie disabled from flying for a while as a result from an injury he suffered when he carried Ducky down a cliff (as the only means of escape when both are cornered by a predator). Cornered later again, with Petrie unable to fly, Ducky has to take him on a dive in a river... Sorry, I'm getting of topic.
Wow, I can't believe I'm the only person who thought sex was the answer right after reading the question!
I cannot point out often enough that the main characters are kids! The movies make very clear that they don't really know about the birds and bees (Littlefoot's question to his grandparents about babies in LBT 2 and his being unaware that every kid in the world would have a mom and a dad in LBT 10). Kids that they are, involving them into this comes very close to something pedophile
Do you want to see that?
The matter is a bit different about the grownup characters and I will readily admit that it is rather unlikely for example for Ducky (the one with an intact family) to have not a clue where her 13 twins are coming from (or the eggs in LBT 2 etc.). I am not in favor of the way LBT has been focused on a very young audience only in some of the recent installations, but I think this topic has to be approached very carefully unless one wants LBT to be turned into dinosaur porn <_<
