Madame Endor |
Characters can rent riding dogs, but small characters can't bond with the same riding dogs as animal companions and use them as mounts.
The Cavalier Dedication archetype class feat, lets you bond with a wolf (other canine may use the stats), but only with the explicitly stated GM permission, and then the feat goes on to say that it doesn't get Mount special ability, which leaves in question whether you can use it as a mount at all.
If you do go with the Cavalier archetype, unlike a horse which can be large immediately, a wolf is small until you take Knightly Steed, unavailable until 6th level.
If you take Improved Steed with Savage as the adjustment, your "riding dog" wolf becomes large sized, which is ridiculous for a small character. It will be two sizes larger than a halfling, gnome, or goblin. Horses that start large, by the way remain large after the Cavalier gets both Knightly Steed and Impressive Steed with Savage as the adjustment.
I don't see anything in the mounted combat rules about mount and character size combinations creating problems, which means that a heavy half-orc barbarian on a medium sized pony have no penalties. It's possible then that small characters could ride a small dog without penalties, but it seems cruel.