Birds do it. Mammals do it. Even caterpillars do it. Whistling is widespread in the animal kingdom. Animals use various means to produce whistles and use their whistles for many different purposes, from warning of predators to calling to a friend. In my latest piece for National Geographic's Weird & Wild news blog, I take a look at some of the wildest whistlers out there, from caterpillars to wild dogs to dolphins.Read the whole story: Whistling Caterpillars and 5 More Surprisingly Musical Species.