Williams-Blangero S.

A recommendation against the use of euthanasia for population control is envisioned as the philosophical basis for managing the US research chimpanzee population in the report on Chimpanzees in Research: Strategies for Their Ethical Care, Management, and Use. This recommendation has major financial implications which threaten the long-term viability of the research chimpanzee resource. The critical need for the continued maintenance of a national resource of chimpanzees for biomedical and behavioral research is clearly outlined in the report. The tremendous costs associated with maintaining this resource indicate that a mechanism for controlling population size is essential. Removal of animals no longer needed for breeding or research to privately funded sanctuaries is one such mechanism. The minority view is that euthanasia is also an appropriate strategy for maximizing the quality of life of the remaining population while facilitating the continued production of chimpanzees to fulfill critical needs in biomedical and behavioral research when faced with limited financial resources and lack of adequate alternative facilities.

The use of the chimpanzee as an animal model has been fundamental to many advances in human health. As outlined in chapter 2 of the document, recent developments pertaining to the control of hepatitis B were dependent in large part upon the use of chimpanzees in vaccine research. The continued threat of current and emerging infectious diseases to public health highlights the importance of maintaining and perpetuating the chimpanzee resource in order to address critical needs in biomedical research. While the present population is sufficient to meet projected research needs over the next five years, if the resource is to be maintained in perpetuity a chimpanzee breeding program will have to be implemented in the future and will result in resumed growth of the population.

Continued breeding of chimpanzees to meet future research needs will necessarily result in further production of surplus animals (i.e., animals not needed for breeding or research programs) because of the practical inability to exactly match sex-specific production and death rates. Demographic and genetic management schemes based on projected demand should be used to minimize the size of the surplus population. However, research demand for chimpanzees is difficult to project accurately and management programs cannot be expected to completely prevent a surplus. Effective mechanisms for dealing with the current surplus animals, and the new surplus animals that will be generated if breeding for biomedical research is continued, are required.

Chimpanzees are expensive animal models, with direct cost per diem rates ranging between $15 (representing a breeding and maintenance facility with no requirements for extensive biohazard containment facilities or intensive research manipulations) and $30 (representing a facility with an active research program involving biohazardous agents). Dyke et al. (1996) have determined that the lifetime costs projected to be incurred for a single animal born in 1995 range between $113,430 and $226,860 for males depending upon the per diem rate, and between $160,860 and $321,710 for females because of their longer average life-span (Dyke et al., 1995).

These high costs apply to all chimpanzees maintained in a colony, including breeders, research animals, and surplus animals that have no potential utility for breeding or research. An alternative perspective on the costs of research with chimpanzees is given by evaluating all the colony costs that go into the production of each individual research chimpanzee. For example, the total cost of producing a naive research chimpanzee includes the costs both of maintaining that animal and of maintaining the breeders to produce the animal. This suggests that the real cost of each research chimpanzee may be substantially higher than the individual life-time cost.

Chimpanzees are behaviorally complex, highly social animals and quality of life issues must be considered in the maintenance of these animals. Non-social housing in barren environments is considered unacceptable for chimpanzees, indicating that sufficient financial resources must be available to ensure adequate enrichment of both the social and physical environments.

The National Institutes of Health Chimpanzee Breeding and Research Program was developed to meet the national need for chimpanzees in biomedical and behavioral research. The breeding program has been highly successful, and there is now a large population of chimpanzees sufficient to meet current requests, and a perceived surplus of animals (i.e., animals with no current or projected utility for breeding or research). The financial resources for maintenance of these animals are ultimately limited and managers are faced with the choice of devoting funds to maintaining chimpanzees with no potential research value, or removing those animals from the colony and utilizing the funds for continued maintenance and production of high quality animal models to facilitate biomedical research with potential public health benefit. Even in the absence of breeding, managers with limited financial resources may have to choose between maintaining a large number of chimpanzees in minimally acceptable conditions which provide for the basic biological needs of the animals, or a smaller number of animals in more humane optimal conditions which allow for both the complex biological and social needs of this species.

Two approaches for managing surplus chimpanzees are compatible with the finite resources available and quality of life constraints. Animals may be moved to other more cost-effective sites, such as private sanctuaries or alternative housing at current facilities, providing sufficient resources are available to maintain an acceptable quality of life. It is not appropriate to use NIH funds in support of animals permanently transferred to private sanctuary housing since there is no potential return on research dollars invested in chimpanzees permanently removed from the research pool.

Alternatively, animals may be euthanized humanely as part of a responsible population management program. As outlined by Lacy (1995) and Graham (1996) for zoo populations, euthanasia allows resources that would be used to preserve animals of limited value to be devoted to maintenance and propagation of valuable animals. In the zoo situation, animals that have already contributed substantially to the gene pool or who are old have little value in terms of species preservation goals and may be selectively culled. As Graham (1996) notes, this management approach emphasizing the targeting of resources to preservation of valuable animals, as opposed to animals with limited value for program goals, should be applicable regardless of whether or not the species is endangered. Selective euthanasia of surplus animals with no potential research or breeding value will free financial resources which can then be used to enhance animal well-being, quality, and research value in a long-term, self-sustaining research chimpanzee population resource. Just as the viability of the species rather than of individual animals is proposed as the primary motivation for management strategies in the zoo situation (Lacy, 1996; Graham, 1996), the long-term viability of the resource for addressing biomedical research needs should be the primary concern in the management of the US research chimpanzee population.

In summary, the minority view is that in the face of limited financial resources, euthanasia is an appropriate mechanism for maximizing the quality of life for the remaining chimpanzee population while facilitating the continued production of chimpanzees to fulfill critical needs in biomedical and behavioral research. It is recommended that an institution inform the NIH interagency animal models committee (or ChiMP office as recommended in this document) of intentions to euthanize chimpanzees and consider terminal collaborative research studies and/or tissue distribution in order to maximize the scientific value of each individual animal.


  • Dyke B, Gage TB, Alford PL, Swenson RB, Williams-Blangero S. A model life table for captive chimpanzees. Am J Primatol. 1995;37:25–37.

  • Dyke B, Williams-Blangero S, Mamelka PM, Goodwin WJ. Future costs of chimpanzees in US research institutions. ILAR Journal. 1996;37:193–198. [PubMed: 11528040]

  • Graham S. Issues of surplus animals. In: Kleiman DG, Allen ME, Thompson KV, Lumpkin S, editors. Wild Mammals in Captivity: Principles and Techniques. Chicago: University of Chicago; 1996. pp. 290–296.

  • Lacy R. Culling surplus animals for population management. In: Norton B, Hutchins M, Stevens EF, Maple TL, editors. Ethics on the Ark: Zoos, Animal Welfare, and Wildlife Conservation. Washington, D.C.: Smithsonian Institution Press; 1995. pp. 187–194.