World building idea blatantly stolen from The Hobbit:
Every in-game race has an ancient alliance with a particular race of wild animals- a species of bird, for instance. Members of this race can automatically communicate with that species or type of animal. Animals of that type are not necessarily the companion or servant of that particular race, they just are cordial with one another and will help each other out if the opportunity presents itself and it isn't too inconvenient. Animals of that type will generally not attack members of their 'ally' race unless the animal is sick or starving to death. Animals of the appropriate type can be negotiated with to provide favors, but they are generally the type of favors that are covered by something the animal would already be likely to do.
Elves - Robins, jays, swans and other similar birds
Gnomes - Burrowing mammals- moles, badgers, groundhogs, marmots, chipmunks
Dwarfs - Eagles; possibly bears
Goblins - Wolves and wargs
Orcs - Carrion crows
Humans - Non-wolf dogs and wild horses; hawks
Halflings - Mice and sparrows
Example Interactions: An elf could ask a blue jay to carry a message to another elf who lives within 1 days flight, or to pass the message on to another blue jay who can pass it on to whoever. A bird is going to be flying around all the damn time anyway, and doesn't need any incentive to pick one place over another. A wolf (who probably spends all day scouting his territory anyway) would tell a goblin when someone new has entered or left the territory he patrols, and what rumors he has heard through night-time howling from other packs. Violent animals might be willing to go along with their allied races in combat, but their goal is slaughter and feeding, not clearly defined strategic objectives. Carrion crows enjoy telling orcs things that will rile them up and get them out killing people because hey, free buffet. More complicated favors (things that involve doing something the animal would not normally do, like carry a rider or a message, fight someone, fly in bad weather would require convincing the same way you would need to convince or bribe a friendly stranger to do something. Particularly animals may become friends with an individual rather than just pleasantly disposed towards a particular race. Hunting or killing a member of your allied animal species gives you a bad reputation and makes it more likely your future requests will be refused.
It also occurs to me that the Alignment languages from the early versions of D&D could be used for this purpose- your ally species speaks the alignment language of your race- Chaotic Good for Elves, Lawful Good for Dwarves, Neutral for Humans, Neutral Good for Halflings, Neutral Evil for Goblins, Chaotic Evil for Orcs, Lawful Evil for hobgoblins, etc.