UV radiation through a hole in the ozone layer depletes its food source, zooplankton. The blue whale is the loudest animal on earth, using low-frequency rumbles to communicate across hundreds of miles of ocean. ...

He heads into the dense rainforest canopy to track down the loudest animal in the world, the howler monkey, a critically endangered primate that's falling prey to poachers. While there, Donald stumbles on his least favorite creature, ...