Progressing my player's animal cohort in 3.5?(pet)

[MonkeySage]

One of my players has adopted an orphaned hound. the dog's previous owner was a 13 year old boy who died exploring a goblin infested cave. through a series of handle animal checks, the dog fights alongside the party in exchange for food, water, and affection. now, I'm wondering how I should progress the animal, since it is neither a familiar nor animal companion.

[eggynack]

Maybe have the player take wild cohort (http://archive.wizards.com/default.asp?x=dnd/re/20031118a) if they want the hound to advance. You could even run it as a riding dog, in that case, if the feat wouldn't be sufficiently appealing if applied to a standard dog.