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9. Gibbon Research and its Changes Over Time


The way scientists are dealing with primates has changed in time. This is shown here in the example of the gibbons, but reflects a general trend.


Up to the first half of this century, our knowledge on gibbon biology was almost exclusively based on reports provided by hunters or on observations carried out on single captive gibbons.

It is often difficult to separate facts and fiction in these reports. For instance, even scientific publications repeatedly cited reports according to which gibbons were living in huge herds of 100-150 individuals. Gibbons were reported to threaten humans in the forest, and even to climb down from the trees, run after humans and attack them (Owen, cit. in Blyth, 1844; Miller, 1778).

As mentioned above, gibbons are usually captured as infants by shooting the mother. Because very little was known on the diet and needs of gibbons, these captive infants rarely survived into adulthood, and captive births of gibbons remained zoo biological sensations up to the 1960s. Even the siamang, which is frequently kept in zoos, was first bred in captivity only in 1962 (Speidel, 1963).

Research on gibbons was typically focusing on their systematics and anatomy, and many gibbon pictures of these days document how little was known about living gibbons, such as their locomotor and positional behavior (Figure 9.1).

 Quadrupedal skeleton reconstruction of a

Figure 9.1. Quadrupedal skeleton reconstruction of a "Gibbon Varié"; probably a Hylobates lar (from De Blainville, around 1841, Plate II).


A.P.E. - On the Threshold to Modern Topics

The Asiatic Primate Expedition (A.P.E.) was the largest but also one of the last expeditions sent out to collect primates for scientific research and documentation (Figure 9.2). It was jointly sponsored by several universities of the United States. The main part of the expedition was carried out north of Chiengmai (in Siam, the Thailand of today). There, 146 gibbons were collected in 1937, more than on any other single expedition. The data collected on these specimens were the basis of a monograph on age changes and variability in gibbons and several other publications (e.g. Schultz, 1944).

Porters of the A.P.E. expedition resting on the way to the base camp north of Chiengmai

Adolph H. Schultz measuring to freshly hunted gibbons near Chiengmai


Figure 9.2. Left: Porters of the A.P.E. expedition resting on the way to the base camp north of Chiengmai (from Carpenter, 1940, p. 25). Right: Adolph H. Schultz measuring to freshly hunted gibbons at the base camp near Chiengmai (A. H. Schultz Archive, Anthropological Institute, Zurich University).

At the same time, the first systematic behavioral study of wild gibbons was carried out as a part of the A.P.E. expedition (Figure 9.3). Clarence R. Carpenter observed and documented the daily life of unhabituated gibbons during three months. In his monograph, he correctly described diet, individual behavior, the monogamous social structure and territorial behavior of gibbons (Carpenter, 1940).

Clarence R. Carpenter observing wild gibbons in Chiengmai

C. R. Carpenter and his parabolic reflector microphone

Figure 9.3. Left: Clarence R. Carpenter observing wild gibbons in Chiengmai; right: C. R. Carpenter and his parabolic reflector microphone. This installation was used to record the calls of wild gibbons on disk, another "first" in the history of gibbon research (from Carpenter, 1940, p. 26).

The A.P.E. expedition documents a paradigm shift in primate research: the end of the great museum expeditions and the beginning of field research.


During the second half of the 20th century, several field studies with durations of one year or more were carried out on several gibbon species. Academic careers are increasingly dominated by the "publish or perish" imperative. As a result, the number of publications on gibbons has been increasing exponentially since about 1950 (see below: Figure 9.7).

Unfortunately, gibbons were not only studied in the field, but also overrun by growing human civilization, in the same time. The survival of many gibbon populations has become endangered by the loss of habitat, but also by hunting pressure (Figures 9.4 and 9.5).

The relic forest of the Ailao mountains of southwestern Yunnan Province (China)

Area south of the headwaters of the Black River in Yunnan

Figure 9.4. Left: The relic forest of the Ailao mountains of southwestern Yunnan Province (China) is the home of one of the last populations of the western black crested gibbon (Nomascus concolor). Right: This area south of the headwaters of the Black River in Yunnan still had some forest populated by black crested gibbons (N. concolor) in historical times. This photograph documents the fate of most Indochinese forests: The whole area is deforested and the soils are visibly exposed to erosion. As a result, the humus layer is being washed away which makes a reforestation impossible for the foreseeable future (photographs: T. Geissmann, 1990).

Weapons confiscated from poachers in the Bawangling Nature Reserve on Hainan island

Infant yellow-cheeked crested gibbons (N. gabriellae) for sale on an animal market

Figure 9.5. Left: Weapons and poached flying squirrels confiscated from poachers during a gibbon survey in the Bawangling Nature Reserve on Hainan island, China (photograph: T. Geissmann, October 1993). The Bawangling Nature Reserve is the home of the last gibbons on Hainan. During his survey, the author estimated the gibbon population at less than 20 gibbons, whereas at least 10 poachers were hunting in the reserve. Right: Infant yellow-cheeked crested gibbons (N. gabriellae) for sale on an animal market near Saigon (photograph: J. Adler, 1988).

Scientific research is exhibiting an increasing interest in the immense biodiversity of tropical rain forests and their relevance for the earth's water supply. This appears to correlate with a growing public awareness that human interference has irrevocably destroyed much of these forests, but also with a growing and justified concern about the potential consequences of this destruction (Figure 9.6).

WWF-Poster by K. Komolphalin (ca. 1983), showing pileated gibbons

WWF-postage stamps from Vietnam (1987), soliciting the protection of crested gibbons

Figure 9.6. Left: WWF-Poster of the Thai artist K. Komolphalin (ca. 1983). The text reads: "How can we survive without forest! Pileated gibbons (Hylobates pileatus) are protected under Thai law but are presently endangered due to forest destruction and to hunting for animal trade - mothers are shot and the clinging baby collected and sold." Right: WWF-postage stamps from Vietnam (1987), soliciting the protection of white-cheeked crested gibbons (Nomascus leucogenys).

Consequently, the main focus of gibbon research during the last 30 years has increasingly been shifting towards (1) ecology / field research and (2) conservation biology / protection of species and of ecosystems (Figure 9.7). The conservation of gibbons and their habitat is increasingly being recognized as one of the most important and urgent research topics.

Changes in the proportions of gibbon research contents during the last 300 years 

Figure 9.7. Changes in the proportions of research contents during the last 300 years, determined on the basis of 2,600 publications on gibbons. Although conservation biology is the last topic to be introduced (i.e. in the 1950's), it is the third most frequent topic of gibbon-related publications. It is only surpassed by ethological and ecological studies, both of which are also increasing in proportion.

The proportions of anatomical and physiological research efforts are clearly in decline, whereas publications on systematics and distribution appear to be on their way out. The impending disappearance of complete research branches, however, is not unproblematic in itself. Based on our current state of research, we are unable to identify most gibbon subspecies without exact information of an individual's provenance, and distribution areas of many of them are not sufficiently known. Because subspecies of even the most common gibbon species kept in zoos (the white-handed gibbon, Hylobates lar) cannot be reliably determined, the zoo population of this species mainly consists of subspecific hybrids since several generations. As a result, these zoo gibbons are now de facto unsuitable for any serious re-introduction projects of rare local populations. This also applies to several other gibbon species. There are also reasons to assume that undiscovered gibbon taxa still exist. As long as they are not discovered, their protection cannot be promoted. Research on systematics is at least as important now than it was in the past.

This is not a gibbon-specific problem. Our ignorance of fundamental systematics directly complicates conservation efforts and their success in general. Different research branches such as conservation biology and systematics are not independent of, but may benefit from, each other. They should equally be carried on and supported.