Costa Rican howler monkeys are the loudest land mammals on earth, making a sound that could commonly be mistaken with the sound of a werewolf howling. They are among the biggest species of New World monkeys in the world, ranging from 16 – 28 inches (40 – 70 cm) not including its tail; although the famed spider monkey is larger, the credit mostly goes to its long arms.
The howler monkey usually stays in groups ranging from six to fifteen. This group usually consists of three adult males, and (commonly) multiple females. The howler monkey uses the loud sounds they make for territory protection inside of the group and to protect and guard their mates. Fighting between howler monkeys is not commonly frequent, especially between different sexes. The duration of the rare fights is usually not long, however, serious injuries can occur. Mostly because of the physical shape of a typical female and a typical male howler monkey.
The famed sound that the howler monkeys typically make are caused by enlarged basihyal, and a hyoid bone. The hyoid bone looks a lot like a mustache attached to the neck, quite far under the skin. Although humans have hyoid bones too, they are not as large and powerful as that of the Costa Rican howler monkey, therefore the reason why we cannot make sounds quite like them. According to the Guinness World Records, their howls can be heard clearly up to two miles away and the volume of the howl is estimated at 128 to 140 dB.
Howler monkeys have roamed Central and South America for many years. However due to habitat destruction and being taken as zoo animals, some species of howler monkey are endangered. As an example, the black howler monkeys, whose population has been declining for many years and are now officially on the endangered list.