Report 50297: Horse boarder hears possible vocalizations late at night west of Belgrade

I used to own a horse boarding facility which was/is located about 3/4 of mile south of the West Gallatin River and about 4 miles north of Belgrade, Montana on the south side of I-90.  One night at around 11 pm I was outside just before going to bed and I heard what I thought was a very loud screams from a woman west of me toward the river.  I was ready to get in my truck and investigate the screaming but the screams were not human.  All of the horses in my boarding pens were snorting and looking west toward the river.  My Australian shepherd dog was also acting very strange; growling and his hair was standing up.  A large number of whitetail deer lived along the river and routinely came down to my place to feed on any hay left over on the ground.  They were a real nuisance. I did not see or hear anything else but I will never forget that sound and the way the horses were acting; similar to smelling a bear.  Even the next morning, Butch, my dog was continually looking toward the river and acting very wary.