Spitting into the ferret's mouth?

I'm really hoping there was some practical reason for doing this; otherwise it was just a baffling and disgusting scene.

Only thing I can think of is the human saliva somehow makes the critter a more effective hunter, considering the character who did the spitting did so just before releasing the ferret into the rabbit hole for the kill.

Still, I'm not sure how exactly it would work.

I should also point out that the "saliva donor" was not actually a member of the original hunting party, and unlike the rest of the characters, showed no signs of losing his mind as the day progressed. So I don't believe madness or mental breakdown had anything to do with it.

Can anyone more knowledgeable than myself shed any light on this?