ELectronic will be a Fox Pro nothing on the market offers what a Fox Pro does. Plus their customer service is top notch. For mouth calls I prefer custom calls by Kettle Creek calls. I have 2 backstabbers and a lil pecker. They are high quality and affordable.
Get tapes of wounded prey animals. They're effective for most predators though, so double check before taking a shot. I've seen foxes, wolves, coyotes, mountain lion, bobcat, bear and all sorts of raptors called using taped wounded prey. My dad was a USDA Forest Service biologist, so I got to go on all kinds of adventures when I was a little kid.
