While most of the time when my BP's are ready to eat they are under their hides with just their head and a little bit of neck sticking out, if they are really hungry and ready to eat, they do a good imitation of a viper. I need to get that on video sometime.
That said, I don't breed my own feeders and I primarily feed f/t, so the only time my snakes smell food is on feeding day. I also thaw the feeders in the herp room to pre-scent it, so they know if the tub gets opened they're getting fed.