Updated.
Let's knock out some more of the basics:
For the attack lines, shall we give him a weapon, or stick with unarmed strikes?
Skills: x
Druid class skills are Concentration (Con), Craft (Int), Diplomacy (Cha), Handle Animal (Cha), Heal (Wis), Knowledge (nature) (Int), Listen (Wis), Profession (Wis), Ride (Dex), Spellcraft (Int), Spot (Wis), Survival (Wis), and Swim (Str).
Feats: 7
Just about anything could work here, although since he can't cast spells, that rules out some common druid feats.
Challenge Rating: At least 18, probably 19
Treasure: Standard?
Advancement: By character class?
The jakar speaks the language of the animal form it has assumed; in human form it speaks any languages it knew at the time the collar was placed on it.
The jakar speaks Common, Druidic, and Sylvan?
Speak with Animals (Su): The jakar can continuously speak with animals (as the spell).