Enriching the Lives of Captive Primates

Linda Brent

The author reviews improvements in the behavioral management of a colony of captive chimpanzees at the Southwest Foundation for Biomedical Research. Environmental enrichment techniques, such as providing increased opportunities for physical, sensory, and feeding stimulation, as well as improvements in management techniques, are discussed.

The Southwest Foundation for Biomedical Research (SFBR), located in San Antonio, Texas, is home to 222 chimpanzees. The chimpanzees play a vital role in the development of vaccines for hepatitis and AIDS. In addition, SFBR maintains a breeding program with approximately 37 active breeders and their offspring. In 1987, a comprehensive environmental enrichment program was initiated and has been expanded to include improvements in management and husbandry. A multifaceted approach that includes consideration of both the social and physical environment has proven to be most beneficial.

Great emphasis has been placed on the importance of captive nonhuman primates (e.g., Novak & Suomi, 1991). Chimpanzees, like most other primates, have adapted to a social setting. With a naturally long period of infant dependency, the chimpanzee is ensured adequate learning opportunities from the mother and other family members in order to function properly in chimpanzee society. In the captive setting, raising nonhuman primates with their mothers in a group composition typical of a natural population is an important component of well-being as well as ensuring the long-range utility of the animal (Mason, 1991). In our colony, every effort has been made to keep the mother-infant pair together in their mixed sex group. This often involves around-the-clock monitoring of new or previously inadequate mothers to give them every opportunity to raise the infant on their own. We also house young females with experienced mothers and infants so that they can observe proper maternal behavior and practice handling infants. In the past, infants had been left in their natal groups for 12 months, but this time period has been lengthened to 24 months to increase the probability of normal social development. Once the chimpanzee is removed from the mother, s/he is placed in a peer group. Chimpanzees designated as future breeders remain in the natal group, or are reintroduced into another breeding unit.

If the infant is removed from his/her mother due to neglect or illness, s/he is placed in a peer group in our nursery. Improvements in the nursery area have been extensive, with the goal of providing more stimulation to young animals. Baby toys, towels, fleece pads, mirrors, activity centers, and climbing structures are available.

The walls are brightly painted with murals, and the infants have a viewing window so that they can see the adults in the adjacent areas. Brightly colored fish swim in a large aquarium next to the young infants. Human contact is also an important source of stimulation. A successful volunteer program has enabled us to offer additional "play time" for the babies, not possible with only the animal care staff.

Older chimpanzees at SFBR are housed in compatible social groups, unless they must be temporarily individually caged for experimental reasons or illness. While on research protocols, most chimpanzees can be pair-housed, and all animals have at least visual and auditory contact with neighbors. Cage size has been greatly increased for our research animals. Recent renovation of most animal rooms included the addition of four large runs, each measuring 50 sq. ft. Two runs are separated with guillotine doors that allow easy pairing or transfers of animals.

Structural improvements for most chimpanzee enclosures include:

  • perches for swinging
  • large resting benches
  • ropes
  • mirrors
  • televisions for those housed indoors
  • a variety of cage toys. We have found that Boomer balls (Boomer Ball, Grayslake,IL) and Kong toys (The Kong Co., Lakewood,CO) are very durable, although Roger Fouts (personal communication, 4/24/92) has found that if an enrichment item is indestructible, it rapidly loses interest for the chimps, and that destructibility or at least the ability to change the item in some way is needed to sustain interest.
    Providing this kind of toy would be more practical in Roger's situation, where there are only a few chimps. We have found surprisingly long sustained interest with durable toys with our chimps.
  • nylon bones
  • tires
  • empty plastic containers or drums
  • inexpensive dog toys

Small toys that may go down the drain are attached to short chains and fastened to the wire cage. Most individuals like to shake the chains as much as manipulate the toys. The young more often engage in play behavior with objects, while the older may use objects in displays. Providing a variety of toys and/or rotating the items helps to decrease boredom with an old toy. Sprinklers and shallow rubber pools are especially popular during the hot Texas summer. Nesting material, such as hay, butcher paper, or toilet paper, are also routinely provided for the chimpanzees. Positive behavioral changes have been observed with the use of woodchip bedding for a group of juvenile chimpanzees (Brent, in press).

In 1989, a large playground was constructed for the breeding colony (see Eichberg et al., 1991, for complete description). Culverts, climbing structures, and grass ground cover are some of the items found in the playground. Horizontal and vertical space may be utilized, and moveable and stationary objects are present. 

While using this area, the chimpanzees exhibited reduced levels of abnormal and self-directed behaviors and increased levels of activity and environmental manipulation (Brent et al., 1991). Construction is now under way for similar housing units for research chimpanzees.

Feeding enrichment is also an important component of the program. Because wild chimpanzees eat a variety of food items and spend much of their day foraging, the goal of feeding enrichment is to approximate more closely those feeding patterns (Bloomsmith, 1989). Most chimpanzees have access to pipe feeders, which simulate the termite fishing behavior of wild chimpanzees (Brent et al., 1991; Maki et al., 1989). We provide browse, such as grass, grapevines, and tree branches when available. Several areas have puzzleboards attached to the roof. Treats are placed on the board and the chimpanzees use a finger to manipulate the treat to a hole that the treat will fit through (see Brent & Eichberg, 1991, for evaluation).

This device is inexpensive and does not interfere with husbandry practices.

The most comprehensive element of chimpanzee enrichment at the SFBR is the daily enrichment program. We provide a wide variety of items to all chimpanzees four to five times per week. Categories of enrichment include:

  • food items including peanuts, garbanzo beans, jello, macaroni and raisins are just a few food items that may be scheduled each month. Frozen liquid or foods offer an interesting and time-consuming alternative to the usual presentation..
  • foraging opportunities
  • human interactions, including playing chase, or blowing bubbles
  • drawing or painting
  • blowing bubbles or playing chase which involve the human in positive contact with the chimpanzee

We provide birthday treats for the chimps, and special items on holidays to add variety. Both the animal care staff and a dedicated enrichment technician have helped to develop this program into an important part of daily life for the chimpanzees.

As part of the improved care of the chimpanzees, initial training and continued educational opportunities for staff members have been expanded to include topics on primate behavior, well-being, and environmental enrichment. Documentaries and nature films have been especially well attended by the staff.

In addition to the enrichment program, new environment or management techniques have also been evaluated. Controlled research designs are usually necessary in order to gain insight into the effects of the captive environment on chimpanzee behavior and development. This allows for an objective evaluation that may avoid problems with anthropomorphic or anecdotal information. Results from studies on enrichment are also available in the form of reviews, journal articles, newsletters, and presentations at meetings (e.g., Petto et al., 1990).

Although we feel that the environmental enrichment program and improvements in animal management have enhanced the lives of the chimpanzees at SFBR, we are striving to do more. The program is not static, and new ideas are regularly tested. Different types of toys, construction of new climbing structures, new foods, and better methods of raising and introducing chimpanzees are some of the issues that keep the enrichment staff busy. Through this multifaceted, dynamic approach, our goal is to meet the changing needs of the chimpanzees and provide an environment conducive to their well-being.


I thank Mollie Bloomsmith for her much appreciated support and guidance. I also acknowledge the input of Mark Bodamer for the initial ideas on the daily enrichment program. The chimpanzees are maintained in the facilities approved by the American Association for Accreditation of Laboratory Animal Care, and in accordance with the regulations of The United States Department of Agriculture.


Bloomsmith, M.A. (1989). Feeding enrichment for captive great apes. In Segal, E. (Ed.). Housing, care and psychological well-being of captive and laboratory primates. Park Ridge, IL: Noyes Publications, 336-356.

Brent, L. (in press). Woodchip bedding as enrichment for captive chimpanzees in an outdoor enclosure. Animal Welfare.

Brent, L., Daley, A. & Martin, N. (1991). Enrichment ideas from the Southwest Foundation of Biomedical Research. The Newsletter: The Primate Foundation of Arizona, 2(4), 2-3.

Brent, L. & Eichberg, J.W. (1991). Primate puzzleboard: A simple environmental enrichment device for captive chimpanzees. Zoo Biology, 10, 353-360.

Brent, L, Lee, D.R., & Eichberg, J.W. (1991). Evaluation of a chimpanzee enrichment enclosure. Journal of Medical Primatology, 20, 12-16.

Maki, S., Alford, P.L., Bloomsmith, M.A. & Franklin, J. (1989). Food puzzle device simulating termite fishing for captive chimpanzees (Pan troglodytes). American Journal of Primatology, Supplement 1, 71-78.

Mason, W. (1991). Effects of social interaction on well-being: Developmental aspects. Laboratory Animal Science, 41(4),

Novak, M. & Suomi, S.J. (1991). Social interaction in nonhuman primates: An underlying theme for primate research. Laboratory Animal Science, 41(4), 308-314.

Petto, A.J., Novak, M.A., Fingold, S.A., & Walsh, A.C. (1990). The search for psychological well-being in captive non-human primates: Information sources. Science and Technology Libraries, 10(2), 101-127.

Reproduced with permission of the editor. Published in Humane Innovations and Alternatives Vol. 6, 1992, p. 371-373.

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