AZA Species Survival Plan Profile


By: Lori Perkins

Orangutans (Pongo pygmaeus) share many characteristics with the African great apes, yet, in several important ways, they are unique among the Pongids. The orangutan is the only Asian representative of the great apes. Although its range once extended throughout Southeast Asia, it is now found only on the islands of Borneo and Sumatra. It is also the only frugivorous great ape, and the only taxon that is truly arboreal. Finally, in contrast to the gregarious chimpanzees, bonobos and gorillas, wild orangutans adopt a semi-solitary lifestyle. These unusual characteristics, combined with a comparatively placid and adaptable disposition, have made orangutans historically popular in zoological collections worldwide.

A Species Survival Plan (SSP) for orangutans was initiated in 1982. The vast majority of AZA-member zoos in North America housing this taxon agreed to participate in the SSP and all orangutans in North America began to be managed as one population. The question of subspecies has, however, been an issue for the orangutan SSP since its inception. A morphological difference between orangutans from Borneo (Pongo pygmaeus pygmaeus) and those originating in Sumatra (P.p. abelii) has long been recognized by both field researchers and managers of captive animals (e.g., MacKinnon 1975; Mallinson 1978; Seuanez 1982). These physical differences are most apparent in adult male animals, and include differences in hair color and texture, facial shape, and cheek flange size. Whereas most orangutans in North America were traditionally managed as a single species regardless of origin, a few institutions did house the two forms separately, based on morphology. As a result of several long-term examinations of the chromosomes of the two forms (Seuanez et al. 1979; Seuanez 1982; Janczewski et al. 1990; Ryder & Chemnick 1993), the SSP in 1985 adopted a moratorium on the reproduction of subspecific hybrid orangutans. Similar moratoria were subsequently adopted by each of the regional orangutan management programs worldwide (Europe, Great Britain, Japan, Australia, and Southeast Asia).

The long history of managing orangutans as one population resulted in a sizable captive population of subspecific hybrid animals. Thus the orangutan SSP program found itself from the start in the position of managing three separate populations of animals (Bornean, Sumatran, and subspecific hybrid). The moratorium on subspecific hybrid reproduction was met with a fair degree of controversy‹some disputed the substantial genetic evidence; others argued that by becoming taxonomic "splitters" the SSP was making its genetic and demographic goals impossible to accomplish; still others accused the management program of treating subspecific hybrid orangutans as "second-class citizens." In the decade since the moratorium, the SSP has worked hard to dispel these misconceptions. The genetic evidence of orangutan subspeciation is so overwhelming that it cannot be ignored. Much as responsible captive animal managers would not interbreed chimpanzees with bonobos, Asian lions with African lions, or the various subspecies of lion tamarins with one another, the SSP does not allow interbreeding between the forms of orangutan (the genetic distances in these examples are comparable; Janczewski et al. 1990). "Splitting" did make the SSP's population goals more difficult, because instead of one large population, it must manage three smaller ones, which makes the genetic and demographic goals much more challenging. However, with careful management and frequent review of the populations' status, those goals are being met. Finally, the point that is consistently emphasized is the fact that subspecific hybrid orangutans are managed according to the same husbandry standards as are the Bornean and Sumatran individuals; there are no "second-class citizens" among the orangutans in the SSP. Subspecific hybrid orangutans are prevented from reproducing by means of contraceptive implants and vasectomies or tubal ligation. Thus such animals can be and are maintained in social groupings identical to those of their Bornean and Sumatran counterparts.

The SSP's goal is to achieve self-sustaining populations of Bornean and Sumatran orangutans that can continue to serve as ambassadors for their wild counterparts and their habitat, as well as a resource for conservation education and research. Specifically, the SSP program presently aims to preserve approximately 91% of original genetic diversity in the Bornean population over the next 100 years, and approximately 94% of original genetic diversity in the Sumatran population. The Bornean population in North America is both smaller in number and, on average, older than the Sumatran; the SSP's management group is exploring the possibility of "merging" the North American population of Bornean orangutans with that of Europe and Great Britain. Most of the individuals of this subspecies would in this proposal remain in North America, but would be managed "as if" they were within the European population. This would enable the management of a larger pool of animals as one population. The demographic goal of the SSP is to "grow" each population to carrying capacity and to stabilize the populations at those levels. More generally, the intent is to combine knowledge of genetics, demographics, husbandry, and individual behavior patterns to best preserve as much genetic diversity as possible in stable captive populations, as both direct and indirect means of supporting orangutan conservation in the wild.

In order to more readily promote the mandate of providing direct support to wild orangutans and their habitat, the SSP in 1995 completed a survey of ongoing orangutan field conservation and research programs in Indonesia and Malaysia. Survey results were sent to all 54 North American zoological facilities that participate in the SSP. These facilities have been encouraged to choose one or more of these in situ projects to which to provide direct support, by means of developing formal or informal partnerships with the field projects. The survey will be updated annually, and the results of this new initiative will be assessed regularly in order to determine how successful the SSP continues to be in providing direct support to the conservation of orangutans in the wild.

A program initiated at Zoo Atlanta in 1995 is being used as one model for how such support can be generated and maintained. Zookeepers at Zoo Atlanta developed a grassroots fundraising program called "Action for Animals." They wanted to provide keepers and educators with a means of contributing financially to a field conservation project, while educating others about the specific issues surrounding in situ conservation. The Action for Animals program uses "Breakfast with a Keeper" talks, recycling programs, brochures, and a host of other fund-raising tools to increase staff and visitor awareness of and involvement in orangutan conservation in the wild, while remaining a low-cost, grassroots effort about which enthusiasm remains consistently high. All proceeds from the Action for Animals program go to the Wanariset Orangutan Rehabilitation Project in Indonesia in the form of equipment and material support. Progress reports, newsletters and updates from Wanariset staff keep Action for Animals participants informed and involved in the program, maintaining consistent levels of support. An important goal of the SSP is to encourage all participating zoological facilities to develop similar programs whereby other in situ conservation projects are directly supported by zoos that house orangutans.

In another effort to promote the conservation and protection of wild orangutans and their habitat, the SSP supported and participated in the first Population and Habitat Viability Analysis (PHVA) workshop for orangutans. This workshop, held in Sumatra in 1993 (Tilson et al. 1993), assessed the current population status of wild orangutans and identified and evaluated threats to those populations. Specific recommendations were made for the critical habitat requirements needed to achieve viability for the wild populations, and for the alleviation or elimination of threats to those populations. While the 1993 workshop focused largely on the Sumatran subspecies, the SSP continues to promote the idea of a second PHVA focused on the Bornean populations.

A short-term goal for the orangutan SSP is the imminent distribution of a comprehensive husbandry manual representing the state of current knowledge of the management of orangutans in captivity, including chapters on enrichment, diet, sociality, genetics, and exhibit design. Another important goal is to continue working with educators to develop more and better ways to educate the visiting public about orangutans and their Asian rainforest habitat, and to explore new ways of demonstrating to zoo visitors the unusual and fascinating characteristics of these unique great apes.

Literature Cited

Janczewski, D.N., D. Goldman, and S.J. O¹Brien. 1990. Molecular genetic divergence of orangutan (Pongo pygmaeus) subspecies based on isozyme and two-dimensional gel electrophoresis. Journal of Heredity 81:375-387.

MacKinnon, J. 1975. Distinguishing characteristics of the insular forms of orangutans. International Zoo Yearbook, 15:195-197.

Mallinson, J.J.C. 1978. "Cocktail" orangutans and the need to preserve pure-bred stock. The Dodo: The Journal of the Jersey Wildlife Preservation Trust 15:69-77.

Ryder, O.A., and L.G. Chemnick. 1993. Chromosomal and mitochondrial DNA variation in orangutans. Journal of Heredity 84:405-409.

Seuanez, H.N., H.J. Evans, D.E. Martin, and J. Fletcher. 1979. An inversion in chromosome 2 that distinguishes between Bornean and Sumatran orangutans. Cytogenetics and Cell Genetics 23:137-140.

Seuanez, H.N. 1982. Chromosome studies in the orangutan (Pongo pygmaeus): Practical applications for breeding and conservation. Zoo Biology 1:179-199.

Tilson, R., U.S. Seal, K. Soemarna, W. Ramono, E. Sumardja, S. Poniran, C. van Shaik, M. Leighton, H. Rijksen, and A. Eudey. 1993. Orangutan population and Habitat Viability Analysis report. IUCN/SSC Captive Breeding Specialist Group, Apple Valley, MN.

Lori Perkings is coordinator of the Orangutan SSP and keeper of the International Studbook. She works at Zoo Atlanta and can be reached at 800 Cherokee Ave. SE, Atlanta, GA 30315-1440. Tel: 404-624-5925; E-mail:

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