Hello!
We did a randomly generated hunt where we killed a feral mastiff called Facemangler in Ring 96. Unfortunately it didn't drop anything, and Boris doesn't care that we killed it.
:(
To add to this:
The signs in the Bounty Hunter's area didn't have any bounties posted on them when we went to turn it in.
I've had the same with a Mastiff variant, perhaps because its skinnable?
I found a named deer that was on his boards, but when dead it was red and skinnable, no item drop.