One of the most fun parts of watching the northern elephant seals at Año Nuevo State Reserve is when a large bull decides to make his presence known on the beach. We stopped by this bull around sunset, since he was really going at it. In addition to pulling up into the posture that they use for fighting -- they get into some serious fights over dominance by pulling up like this and swinging their necks at each other, then when they make contact, they bite and tear with those big teeth -- they make a unique vocalization that can be heard from quite a distance away. It's sort of like a burping/gurgling sound, but thanks to my wife I don't have to try to describe it better, since she took a video clip while we were on the beach.
As you saw in the video, once they are done displaying, they'll flop back to the ground and look rather peaceful again. This makes for some interesting poses as they come back towards the sand, and I think they look kind of cute with that droopy face.