My Sheltie Kenna loves a good bark as much as the next Sheltie. However she is also very ball motivated. She frequently manages a good bark while holding a tennis ball in her mouth at the same time. I've never noticed any of my other dogs doing this but Kenna has it down to a fine art. She can even make a squeaky toy sqeak while barking. Does anyone else have a dog that barks with it's mouth full?