I've had reds and greys both come running in after howls. I don't understand it...perhaps they were fox with huge balls and a chip on their shoulder?
I start all my sets in my area with rabbit distress. 85% of the time it's all I use, because within the first ten minutes something is running in. I've also discovered it's possible to shoot a red fox and have a coyote run in right after. Since it's late in the season, though, my hand calls change. I'm using odder, or unique sounding distress calls now, like Verminators.