Social Housing for Nonhuman Primates Housed in Captive Settings in the United States

This policy statement was written by members of the ASP Primate Care Committee. It was originally approved by the ASP Board of Directors and published in November 2014, and was revised and updated in March 2025.

Background: The ASP Primate Care Committee formulated the following policy statement to provide a public document regarding the ASP’s stance on social housing for nonhuman primates in captive settings, especially those used in research. There is considerable scientific literature on social housing in captive primates, and best practices will continue to evolve. Therefore, this policy statement does not address specific scientific findings, rather it articulates general principles held by the society. The scope of this policy is on primates in the United States. Other countries may have a different set of regulations. These guidelines build upon the ASP’s 2001 Policy Statement “Principles for the Ethical Treatment of Non-Human Primates” which states that ASP members “should make use of information on a species’ natural history to improve management and enrich environments, because physical and psychological well-being are essential not only to the health of the animal but also to the validity of the research results.”

Policy Statement: The ASP endorses social housing as the foundation of welfare for captive nonhuman primates (NHPs), and should, therefore, be their default form of housing.  Published research firmly establishes that socially housed NHPs experience superior degrees of welfare to that of their singly housed counterparts. Similarly, introducing singly housed NHPs into a compatible social setting improves their welfare as evidenced by several behavioral and physiological measures. For example, social housing reduces the expression of abnormal behaviors, promotes species-appropriate activities, enhances biological functioning, and provides a buffer for individuals from stressful events. 

This endorsement is consistent with the positions of the United States Department of Agriculture (USDA), the Office of Laboratory Animal Welfare (OLAW), and the Association for Assessment and Accreditation of Laboratory Animal Care International (AAALAC). The USDA Animal Welfare Act (AWA) regulation 9 CFR 3.81, states that plans for environmental enhancement must “address the social needs of nonhuman primates of species known to exist in social groups in nature” (USDA, 2013, p. 100). Public Health Service Policy (2002) states that, “The living conditions of animals should be appropriate for their species and contribute to their health and comfort” (OLAW, 2002, p. 5). OLAW has articulated its view on NHP housing in a policy statement affirming that “like all social animals, nonhuman primates should be socially housed”. Furthermore, AAALAC endorses social housing as the default approach for NHPs, accrediting only those facilities that meet the standards outlined in The Guide for the Care and Use of Laboratory Animals, i.e., “Social animals should be housed in stable pairs or groups of compatible individuals unless they must be housed alone for experimental reasons or because of social incompatibility” (National Research Council, 2011, p. 64).

To this end, implementing a social housing program for captive NHPs across settings requires special attention to overcome challenges and obstacles. The ASP concurs with the following statements:

1. Appropriately implemented social housing should be guided by species-typical social structure. However, it can also benefit configurations that do not replicate social groupings in the wild (e.g., pairs vs. groups). Ideal configurations may not be feasible given the number or age/sex class of research subjects, or because of constraints related to study design, available housing, or clinical condition. However, the least restricting form of social experience should be employed whenever practical since increased social and environmental complexity is associated with better welfare. While permanent, unrestricted social housing is recommended, intermittent social housing for some portions of time or providing a limited degree of social contact is considered superior to individual housing.
2. Formation and maintenance of social groupings can involve risks to animal health and wellbeing, and should be overseen by individuals with expertise in NHP behavior. Animals housed socially require ongoing monitoring to ensure compatibility and reduce the possibility of injury or distress, as social compatibility may change over time, due to intrinsic and extrinsic factors. However, it is recognized that even experienced personnel may not be able to manage social interactions in such a way as to avoid all conflict or injury among the animals and that agonistic interactions, including those that result in wounding, are species-typical behaviors. Moreover, in socially housed NHPs, wounding may arise not only from agonistic interactions, but also from positive or neutral interactions, such as play or mating.
3. In research settings, housing must consider the research use of individual NHPs. Institutional Animal Care and Use Committees (IACUCs) play a pivotal role in this process and ensure that scientific justifications for restricted social housing are robust and evidence based. Therefore, IACUCs must have access to the necessary expertise and should consider including at least one member with advanced training (i.e., Ph.D.-level expertise) in NHP behavior and management on the committee. IACUC-approved exemptions from social housing (including enabling part-time social housing, or tactile contact through a barrier that prevents entry into a partner’s enclosure) should be limited to study phases in which scientific justification for the social restriction applies. The implementation of social housing requires close coordination between behavioral management staff, veterinarians, and research personnel. 
4. The need for single housing in research settings should not be assumed. It has been repeatedly demonstrated that even research involving the application of experimental appliances (e.g., telemetry implants, head caps, eye coils, tethers), the administration of substances exerting psychosocial effects, in protocols studying infectious diseases, or use of restricted/controlled diets, can be done successfully on socially housed subjects. Indeed, evidence suggests that socially housed NHPs generate distinctly different, less variable, and more reliable data than singly housed primates. The need for single housing, or restriction in social housing, should be evaluated using available literature, or, where lacking, awareness of practices and outcomes across facilities. 
5. The AWA exception from social housing relating to individuals exhibiting ‘vicious or overly aggressive behavior’ or debilitation should not be applied to broad classes of individuals or species unless supported by published literature or other performance outcomes. Objective criteria should be established for deeming individual animals excepted for these reasons. This exception should be reviewed routinely to identify opportunities for adequate social interactions.
6. Anticipated financial constraints or lack of resources such as appropriate caging do not justify failing to provide social housing. Furthermore, despite the widely held belief that social housing is costly, the prolonged use of single housing is likely to involve higher costs due to lifetime care. Single housing often requires increased behavioral management and veterinary services to address compromised welfare, treatment of behavioral abnormalities that may develop, and adverse impact on research if behavioral abnormalities are severe. Higher variability in data also requires using additional animals in research, which can lead to higher costs.

References

Association of Primate Veterinarians’ Socialization Guidelines for Nonhuman Primates in Biomedical Research. 2019. Journal of the American Association of Laboratory Animal Science 58(6), 753-754 Retrieved from https://pmc.ncbi.nlm.nih.gov/articles/PMC6926400/ March, 18, 2025

National Research Council. The Guide for the Care and Use of Laboratory Animals, 2011.

Office of Laboratory Animal Welfare position statement on nonhuman primate housing. Retrieved from http://grants.nih.gov/grants/olaw/positionstatement_guide.htm#nonhuman June 2, 2014.

Public Health Service Policy on Humane Care and Use of Laboratory Animals. United States Department of Health and Human Services, Washington, DC, 1986; amended 2002.

U. S. Department of Agriculture.  Animal Welfare Act and Animal Welfare Regulations. Section 3.81 – Environmental enhancement to promote psychological well-being.  Animal Welfare Act and Animal Welfare Regulations (“Blue Book”) 2013.