Nov 062009
photo provided courtesy of jimbowen0306 on Flickr Creative CommonsHomeSoutheast Asia
Habitattropical forest
Nichelarge omnivore (primarily herbivore)
Favorite Foodleaves
Heightup to 5 feet tall
Weightup to 33 pounds
StatusVulnerable to Extinction
Threatshabitat loss, poaching

It’s morning in the jungles of the Malay Peninsula in Southeast Asia. Among the thousands of animal calls fighting for ear space in the dense forests, one stands out among the rest. Indeed, this animal’s deafening call would drown out even the roar of the African lion if put to the test. Able to be heard for over two miles through dense rainforest, the call of the siamang is the loudest of any land mammal on earth.

The siamang is a member of the gibbon family, a group of small, tree-dwelling apes that are known for their spectacular leaps and unrivaled agility among the dense upper canopy of the Asian rainforests. Swinging through the trees with a 5-foot arm span, the stocky, broad-chested siamang is the largest gibbon. These shaggy black apes live in the rainforests of Malaysia, Thailand, and Sumatra, sharing their range with a number of other gibbon species in the treetops.

The most striking feature of the siamang is the expandable flap of stretchy skin on its throat. The skin can be inflated the size of the animal’s entire head and acts as a resonator chamber, amplifying the piercing calls of the ape to ward off intruders and attract mates. The noisesome calls are primarily used to frighten other siamangs that have stumbled into a family’s territory, which can range up to 115 acres.

photo provided courtesy of Lara604 on Flickr Creative CommonsLike other gibbons and great apes, siamangs are social animals, forming small groups of around 5 animals. These family units are very cohesive, and a family member will rarely venture farther than 100 feet from its kin. As with other apes, grooming is the most important social bonding activity with siamangs. However, social interaction between the family unit is kept to a minimum, leaving most of the day open for eating and resting. Leaves are the siamang’s primary food, forming over half its diet. Fruit and insects form the other half, with some regional variation. Half of the siamang’s waking period from dawn until dusk is spent reasting in the trees, taking short siestas in between foragings.

Siamangs are monogamous, meaning they only mate with one partner during the 2-3 year mating cycle, and the mating pair remains together for life. As is the case with other monogamous mammals, there is very little difference between the sexes in terms of body size. Siamangs show an unusual amount of paternal care for a mammal, and the fathers take over care of the infant after about a year. Indeed, the adult male siamang is responsible for a juvenile’s increasing independence on its journey towards adulthood.

After about eight years of family care, the sexually mature siamang is eased out of its family unit and must strike out on its own. Males then begin a period of wandering in search of females and will call out into the forest to find a mate necessary to build a new family. In fact, the loud “singing” of siamangs is an important part of forging and maintaining the crucial pair bonds.

As the forests fall in the Malay Peninsula, so do the siamangs. As illegal logging, clearcutting, and palm oil plantations increase, the future of these magnificent apes grows increasingly in doubt. Without the trees to support them, the siamang’s call will go silent.

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