Do pets gain experience when being ridden?
If I'm riding my Pony will he gain experience and eventually become a Horse (and then a Warhorse)?
Ridden pets level up as normal - by killing monsters. Note, however, that ridden pets are more docile. They will not attack a monster unless attacked first. Since monsters will randomly attack you or the pet when you are mounted, this may mean your pet gets fewer kills (and thus experience) than it otherwise would.