Eh, as of right now the only thing it drops that's worth anything is the meat, which will float. The scales are kinda useless since all they make is a tower shield. But that may change with H&H, since the shields are getting reworked.

But yeah, night storms seem to be the only time I ever see them, and very rarely do I find them in the same spot. Usually I Mark the location on the map when I find one, just to check at a later date. I don't recall finding one in the same place.