the meaning of “truffling grunts”

Question

The Tower is like a small town and its morning routine clatters on around him, the guards and the men from the Mint greet him, and the keeper of the king's beasts trots up to say it's dinner time – they eat early, the beasts – and does he want to see them fed? I take it very kindly, he says, waiving the pleasure; unbreakfasted himself, slightly nauseous, he can smell stale blood and from the direction of their cages hear their truffling grunts and smothered roars.

— Wolf Hall by Hilary Mantel

I looked up a few dictionaries but couldn't figure out what the "truffling" means here.

Answer 1

Understanding this phrase requires some additional knowledge - specifically the existence of the edible fungal delicacy known as a Truffle and the method of acquiring said fungus most well-known in popular culture: sending out trained pigs, a practice known as 'truffling'.

With that information, it is readily apparent that 'truffling grunts' are simply the sort of noises you'd expect to hear from a pig with its snout in the ground searching for truffles.

As the animals are being fed in the snippet you provided, their snouts are indeed likely to be be in a similar position to the truffling pig (just with food instead of dirt), and so make similar noises.