Howler Monkeys

It is the year of the fire monkey! Let’s celebrate with some magnificent screaming monkeys from Central and South America. These monkeys are loud–really loud. They are louder than Rush Limbaugh or heavy machinery–so loud that, in fact, that they are generally regarded as the loudest of all land animals. I am talking, of course, about the howler monkeys. These fifteen species make up the genus Alouatta (which lies within the family Atelidae ). They are new world monkeys ranging from the top of Central America down through South America to Uruguay.

Howler monkeys have short snouts with keen noses (they are capable of smelling their favorite fruits and leaves from 2km away). Depending on the species and gender they range from 56 to 92 cm (22 to 36 in) in height or length…or whatever primary dimension you attribute to monkeys. This measurement does not include their tails which can be up to 5 times the length of their body. They weigh 7 to 10 kg (15 to 22 lbs) and live up to 20 years. Howler monkeys are folivore–they mostly eat leaves. This diet is widely available but it is hard to digest–which means howler monkeys are larger and slower than other New World monkeys (although they supplement their diets with fruit and eggs when they can).

The hyoid bones of howler monkeys are pneumatized–which is to say that the u-shaped bone in the monkey’s neck contains air. Outside of the dinosaurs and their descendants, pneumatized bones are exceedingly rare. The hyoid bone anchors the tongue and the larynx and allows for vocalization. The fact that it is specialized in howler monkeys is one of the factors which allows them to vocalize with such ferocious power. There is an inverse relation between the size of the hyoid bone and the size of the male’s testes. This seemingly random fact is actually a key factor in howler society.

Howler monkey lifestyle diverge into two very different ways of living (except for mantled howler monkeys which live together in large groups and behave somewhat differently than the other 14 species). In one model, a male, who has a larger hyoid, and smaller testes gathers a group of females together with his majestic singing (screaming?) voice and he mates with them exclusively like a sultan with his harem. In the other model several males mate with a group of several females. Seemingly, this free love model requires less loud singing and more gonad mass.

At this point you are probably wondering a great deal about the howler monkey song. What is this primal howl which female monkeys prefer over carnal joy? Musical enthusiasts have compared the baritone shout of the male monkeys to a Gregorian chant, a monstrous belch, or a demonic snowplow.  All of these comparisons have some validity…but the sound is so much richer than that.  Why don’t you have a listen (at 1:23) and let us what you think?

 

Spring Gobbling

Domestic Tom Turkey Gobbling (Photo by WildImages--Charlie Summers)

It has been a long time since I put up a turkey post.  In a way this is appropriate, since people other than hunters and farmers usually only think about the majestic fowl around holiday time when the sharp axe comes out (or–more likely—when one wanders over to Krogers to check out the price of Butterballs).  Meanwhile live turkeys have been slogging away through the long winter.  For farm turkeys this has meant dull days perched in dark coops huddled together for warmth while living on daily water and grain hand-outs from the farmer.  For wild turkeys the winter is more like a Russian war novel.  The wind, ice, and snow are enlivened by desperate hunger and by fear of omnipresent predators stalking through the bare trees of the frozen forests.  The cold nights are filled with the howl of the wind and the coyotes while the days are filled with desperately scraping the dead ground for remnants of food.

But that was winter–spring is here, and with it, mating season.  This time of year highlights one of the signature features of turkeys wild and domestic—gobbling.  In fact today’s post is really an auditory one.  Here is a movie of a Tom turkey gobbling!

The gobble is rightfully the most famous turkey vocalization.  It is similar in nature to the humpback’s song or the deafening yodel of the siamang: a magnificent declaration of self which proclaims dominance and health to females. This ululating yodel alerts all nearby hens to the fact that an alpha male tom turkey is in the area and is at the top of his game (it also lets rival males know where to go for a fight and hunters where to go for a meal, so it is a true and heartfelt declaration of bravery and lust on the part of the issuer).

Gobbles are hardly the only turkey vocalizations.  Turkeys both wild and domestic are extremely garrulous characters and produce many different calls for a variety of reasons.  Here is a list of the more common turkey vocabulary from the national Wild Turkey Federation.  By using a variety of tools and the full range of the human voice a tiny number of truly expert hunters can produce most of these noises, however turkeys are clever enough that they don’t usually fall for such guile.