Belgrade-area resident Alisha Novotny tells a local television station that she noticed her mare, Raz, was missing the hair from her tail last Sunday morning.
She says it looks like whoever did it "just grabbed pretty fast and chopped."
Novotny says horse hair can be valuable - especially white hair like Raz's - for making belts and bridles and key chains. She says she felt "violated" when she realized a stranger had been in the horse's pen.
Gallatin County authorities say this isn't the first time a horse owner in the area as found an animal missing hair from its tail. Officials with the Belgrade Police Department say it's been an ongoing issue for about six months.
