Siamangs are the largest type of gibbons. Gibbons are an ancient group of apes closely related to the orangutan, gorilla and chimpanzee. Siamangs are relatively inactive for several reasons: the nature of their diet - the low nutritional value of the leaves which form the bulk of their diet - and the amount of energy to expel toxins consumed with their natural diet. They spend most of their time in trees foraging for food, where they use long powerful arms to move from branch to branch. When on the ground, they move awkwardly on two legs, with their long arms used to maintain balance. Siamangs are monogamous, usually remaining in one long-term relationship during their estimated 35-year lifespan. A pair usually produce their first offspring at around age nine and then, on average, produce a newborn every three years. The parents take care of the offspring together. Initially the mother devotes more time to the newborn infant, but at age eight months, the father increasingly takes on more care tasks and in fact gives the baby to the mother only during lactation.
In the Zoo, the couple 'Elliot' and "Malaka" were the first to produce offspring in the zoo, after it moved to its present location in Malha in 1993. The infant’s name was “Tov” and since he was born in 1993, three further male siblings have been born. When Tov reached the age of six, he was rejected by his parents who were busy caring for two younger brothers. The rejection process is natural and is designed to allow the teenager to "go out into the big world" and find a mate of his own. At the end of 2010, Elliot and Malaka were retired to a behind-the-scenes exhibit in order to make way for a younger couple to reproduce. Bin-Zhao from Lisbon Zoo in Portugal and Richard, a sabra born here, now live on Siamang Island. Elliot and Malaka can no longer reproduce and, because Siamangs belong to an international breeding and conservation program, it was decided that it was time to allow young Richard and his partner to produce a family. In 2016 the couple had a beautiful infant who can be seen with them on the island.
The siamang exhibit is located at the entrance to the Zoo and their morning “song” welcomes visitors. These calls are designed for communication between individuals and neighboring groups to transmit information. Each family member has it’s own role in the song. Their song is thought to be a declaration of territory, for the strengthening of the family bond, and as a tool for assessing the condition of each individual group. Siamangs live in dense, shaded forests and so good communication is critical. Their voices can be heard throughout the forest, mainly because of their inflatable throat sac, designed to increase the intensity of calls by producing a sort of echo chamber effect.
Siamangs, as well as many other species living in their region, are now endangered due to the destruction of their habitat. The Jerusalem Biblical Zoo cooperates with the European Association of Zoos and Aquaria (EAZA) in its efforts to maintain a healthy captive population to ensure that the species is stable.