Most animals with a predator-carnivore prefix including [bonecarnivore] and [largepredator] should be able to strip the bones at a speed between weight differences of the animal eating and (hopefully not reanimating, in which case eat a bit faster if you please) dead.
Bone carnivores could eat everything except for about 90% of the total animal (after splitting the corpse up into loose fragments of bone it wont eat and 50/50 chance of a skull/horns) whereas regular large carnivores should stop at the late skeletal stage and move onto the next available corpse in the area it can path over as a low priority behavioral job unless pastured. Advantages to this are that it disposes of sentient bodies (Of your dishonourable dwaves, elves and goblins particularly) and rotten corpses left to languish in the sun where they don't contaminate but are a eyesore.
Butchering animals is still the most respectable & efficient way to gather bones in addition to meat and leather, but sometimes circumstances are difficult, and you have to toss the animal or parts of a animal away that rot in the shop or via transit.
Ravens for instance are a excellent example, add the tags for bone carnivore + currently benign and you'd have a skittish carrion eater that goes after and paths to most dead animals to strip them clean. Unlike something large and powerful like a polar bear or a exceptionally sized giant dingo (the near ultimate bone-carnivorous animal for waste disposal next to live captive/pet tethered trolls) it'd take a while for a raven to pick clean a body in the open air such as the remains of a goblin siege.
Putting it one way or another, taking defunct and non-breeding/gelded animal members (because of rampant breeding in close quarters) and getting them to work on something else beside the meat industry (giant rats and naked mole-dogs come to mind due to low pet/fighting capability due to lifespan and skittishness) is a good thing, and should they die of old age down there in that forbidden pit of death, they will only add to the pile to throw more in until the time comes to clear it out via dwarf labour or a swift smack of a bridge.
Could even make a carp/shark/sea serpent waste pond and send them to Urist'Jones Locker if you wish to be ambitious about your projects or are tired of things rotting in the moat (dwarves particularly)
ADDITIONAL READING> Hungry creatures Author - Geldrin (September 04, 2013) *Note - Admittedly very similar to my current suggestion upon reading, i however differentiate in that i have expanded my suggestion in a number of different directions and that I don't agree personally with the implementation of detrivorous behavior mechanics for being game breaking.
> Realistic Creature Behavior Author - franti (July 26, 2011) *Note - Lots of excellently worded suggestions therein, referenced for the section on eating and animal corpse stripping, as to what i can say about it {Giant Elephant - Ravenous - [HERD/PACK] - Specific Food = Dwarf Meat/Fat/Bones }
> New Creature Behavior -- Scavenger Author - rylen (November 29, 2007) *Note - Interesting discussion of using a separate classifying tag and applies examples
> Growing fish Author -jei (September 18, 2010) *Note - The thought of rearing stronger, larger animals on a diet of carrion is appealing, much like keeping a infamously named pet giant spider (thinking Shelob) or a enormous ravenous genetically enhanced breed of pike in a moat
Feedback or additional links would be most appreciated; thanks for reading.