First, Maggie was rescued when Gibson was (and I love this line) "sitting on a snow bank practicing his turkey calls" (how many kids have you heard of practicing Playstation while sitting on a snow bank?). By all accounts, Maggie is nearly deaf and can't hear when her owner is calling to her from a short distance. Turkey calls however, are higher pitched and carry farther. Dogs hear at a higher frequency than humans. I'm betting that Maggie could hear the calls in her makeshift den for just that reason. It's something to keep in mind when you're looking for a dog; high-pitched whistles and calls could be more effective.