A rummele’s charisma is 19 with respect to other canids (dogs, wolves, etc.), including intelligent or magical beasts like winter wolves, and it can communicate with any dog, wolf, jackal, or fox.
Though it is voiceless in its natural form, the rummele has telepathy (as per the psionic discipline).
Feats: Deflect Arrows (B), 2 more
Lycanthropic Empathy (Ex): In any form, lycanthropes can communicate and empathize with normal or dire animals of their animal form. This gives them a +4 racial bonus on checks when influencing the animal’s attitude and allows the communication of simple concepts and (if the animal is friendly) commands, such as "friend," "foe," "flee," and "attack."
Cleon's feat alternatives are fine if we want to go the combat route (Reflexes over Expertise, though, somehow feels better). I wasn't terribly happy with my suggestions in the first place.
Canid empathy would be good, except shadow mastiffs are Outsiders (as GrayLinnorm pointed out). Do we want to include the Outsiders, like hell hounds and yeth hounds? Somehow that doesn't seem quite right.