From experience: A good momma cow can get those ear muffs off in seconds. Duck tape is awful hard to remove without pulling a bunch of hair.
My solution: Go to a fabric store and buy two feet of sweat shirt material or fleece type material. Sew it into a loop (Make like a neck kooze type of thing) Then in cold weather pull it over the head to push the ears flat against the head. Adjust size with safety pins. Works great and cheap, even though a good momma cow can still remove, but a bit tougher than the ear muffs.
Good Luck