What’s that sound? If you hear a deep grunt or growl in the early morning or as the sun goes down, don’t be alarmed. That’s just a howler monkey letting the other monkeys know they’re in his territory. Much louder than a simple “no vacancy” sign, these howls can he heard up to three miles away. Howler monkeys have the claimed the titles as the loudest primates because of their unique enlarged hyoid bone which expands in their throats. They live in the jungles of Central and South America so be on the lookout on ourCosta Rica & Panama Cruises as well as spider and squirrel monkeys, white-faced capuchins, Baird’s tapir, and two- and three-toed sloths.