Mountain lions are able to whistle

Mountain lions, also known as cougars, are actually able to whistle. While they are commonly quiet in the woods, sneaking up on prey through the bushes, mountain lions can choose to whistle, which sounds a lot like either a bird chirping or a human being whistling. So if you find yourself in the middle of the woods by yourself and you hear someone whistling, it might be better to mind your own business.