Species: Siamangs (Hylobates syndactylus)

Use: Protective and Territorial Behavior

Authors: Mathias Orgeldinger

Methods: Ad Libitumpli Samng, Focal sampling, Scan sampling

Publications/Presentations: Mathias Orgeldinger (1997). Protective and Territorial Behavior in Captive Siamangs (Hylobates syndactylus). Zoo Biology, 16: 309-325

Protective and Territorial Behavior Patterns

Vigilance: Can be described as intensive watching near the boundary toward potential rivals (e.g., neighboring conspecifics, other animals, keepers, docents). It is often attended by “tense grimace,” a special form of bared teeth that is characteristic of emotional conflicts [Orgeldiger, 1994].

Display: If the threat to the individual or the territory increases, siamangs show different forms of display behavior such as “piloerection,” “stereotyped brachiation, or swinging,” “pirouetting,” or “bipedal running” with raised hands. Predictably, each individual shows different forms or combinations of display behavior. One male, for example, that lives on an island in the Branféré Zoo, swings a twig up and down with his hand or throws it away during bipedal running. Other individuals shake a chain or other objects that make noises. In contrast, “three-dimensional display” is shown by all adults at the end of the “great call sequence”of duetting. A few individuals, however, show it even in the absence of calling. It can be described as a short, wild, and noisy brachiation in the cage or the top of the tree.

Threat: Threat behavior in a protective and territorial context is also shown in different forms. “Staring” is a directed watching without bared teeth. It can be interrupted by repeated looks in a neutral direction. The same conflict of motivations is expressed if an animal alternately directs “open mouth threat” or his back to a rival. Other forms of threat behavior are “head nodding,” or “body swaying while standing,” which can be accompanied by genital presentation (males only). The most common form of threat behavior is the nondirected or directed “threat biting,” followed by the “aggressive biting of an object.”

Alarm: If captive siamangs are frightened by uncommon situations or noises, “alarm calls” can be uttered. They differ from normal calling behavior by the absence of the complete “great call sequences.” This extremely rare form of loud calls occurs in the late afternoon or at night; during these times the motivation for duetting seems to be diminished.

Attack behavior: In some cases display and threat behavior graded into physical attacks such as “aggressive jumping” against the grating, or “aggressive grasping” through the grating toward a person. Each keeper knows that such attacks can lead to very serious injuries if there is no safety barrier.

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