Non-human Primate Enrichment Evaluation Program

By:  Collin R. Deugan; Arlene A. Gross, RLAT*


Stereotypy is something that every institution deals with when it comes to non-human primates.  Industry wide a struggle exists to find the right treatment, the right environmental enrichment, and the correct social group to alleviate some of the issues presented.  Stereotypy is defined as the persistent repetition of an act for no obvious purpose.  These acts can include pacing, weaving, spinning, flipping and more.  When reviewing current procedures and treatments for stereotypy, a new approach was evident to tackle the problem at the source.  At our facility we utilize a committee to look at suggested enrichment items, where item cost, animal welfare concerns, and feasibility are carefully considered.  Taking that process a step further, the non-human primate enrichment evaluation program gathered data on the novel devices directly from the animals.  A scoring system with ratings from one to five was developed, looking at five different areas to help to determine if a device was worthy of consideration for use in our facility.  Areas considered and scored were percentage of time used, wear and tear, mastery, behavioral changes, and impact on social dynamics.  Selecting animals with compatible, established social groups that included individuals with stereotypy and without, both facility accepted devices, as well as new enrichment devices were scored to determine their viability at the facility.  Quickly it became evident that the new enrichment devices were received with greater appreciation by the animals than the older, established toys.  The older, approved devices were noted as being viewed as a part of the cage, rather than enrichment, whereas the new devices offered opportunities for foraging, game play, brain exercises, and naturally allotted behaviors.  While some of the new devices failed to live up to our expectations, others far exceeded preconceived notions.  Shining light on new ideas that would direct us to change the types of devices utilized, as well as how often devices were given and rotated for the non-human primates’ well-being.



Combating stereotypy in non-human primates is an ongoing endeavor.  Every effort is made to provide the animals under our care with proper enrichment and external stimulation to encourage a well-acclimated and calm animal for the research environment.  Promoting animal welfare is at the forefront of our minds, and following guidelines from various entities, it is paramount that a program is developed that will afford the animals with the most appropriate and safe environment.  Housing the animals in socially compatible groups, allowing vertical access as appropriate, and environmental enrichment are all areas utilized to combat stereotypy.  The development of the non-human primate enrichment evaluation program (NHPeep) was a means to provide animals with proper enrichment, engaging them for species appropriate time allotments, and not only allow, but also encourage species-specific behavior.

Noting that it is typical for enrichment devices to be approved by a committee, and understanding that this is paramount for animal safety, we began to think outside the box and seek additional ways to approve enrichment devices for the non-human primates at our facility.  We created a program that would allow the animals to have a voice in their enrichment device selection.  A scoring system was created as a means of tracking objectively how the animals interacted with the various devices.  New enrichment devices were either purchased or created in-house to serve as our pilot program devices.  Thus, giving rise to the program we now refer to as NHPeep.


Caitec® Baffle Cage: Otto Environmental –item CT 600197

  • Shake-A-Treat:Bio-Serve –item K3350
  • Butcher Paper (12” width): Uline–item S-11458
  • Horizontal Paper Cutter (12” width): Uline–item H-345
  • Various fruits, vegetables, nuts and other healthy food options




Over a period of seven weeks, animals were observed and scored on the interactions with each other and their enrichment devices. Our first week of observations were with previously approved enrichment devices that included mirrors, metal triangles and jingle balls without washers (Figure 1). These items were scored to serve as a baseline. The remaining timeframe was spent scoring the animals with novel enrichment items. Scoring was used to evaluate the devices’ durability and ability to reduce stereotypical behaviors and impact on social dynamics, the animals’ ability to master use of the device, and the amount of attention focused on the device. Scores were given a value of 1 to 5, where a score of 1 represents low values and 5 represents most acceptable outcomes. In the case of destructible items, for device mastery and wear and tear, scores of 1 and 2 were acceptable due to reduced frustration.

Items were offered 5 days a week to socially compatible pairs or trios of cynomolgus macaques, with approximately half of the social groups exhibiting some form of stereotypy. Enrichment devices were offered to the social groups for up to 5 days before being rotated. Toward the end of the novel enrichment experiment, items were rotated daily (Figure 2). Scoring was done at the same time each day and was conducted for no more than 5 minutes per social group. Observations and scoring were performed from an observation suite with one-way glass without human/animal interaction. (Data collected in Figure 3)

Ten individuals who were trained to perform the necessary observations and scoring activities carried out scoring.  Animal care and use was conducted in alignment with animal welfare regulatory requirements in an AAALAC-accredited facility with IACUC approval.


Stereotypic behavior was reduced within ten days from the initiation of novel devices. In most cases, the novel enrichment devices reduced stereotypies to the point of being absent. NHPs were more interactive with each other, their enrichment devices, and their cage environments. Destructible devices tended to result in increased device use, as well as a perceived increase in cognitive response to environment and dietary enrichment. Devices that were sturdy and of sound design proved to be perfect for use with NHPs, as they were able to withstand the force the animals imposed upon them. Social dynamics were strengthened and allowed the animals to express cooperative feeding and foraging. The addition of dietary enrichment daily did not influence the animals’ weight.

Figure 1. Graph of the average score of established enrichment device use.

Figure 2: Baffle Cage, Shake a Treat

Figure 2: Paper Burrito, Baffle Cage

Figure 3. Graphs of average scores for various novel enrichment devices:  Baffle Cage With Only Food

Figure 3. Graphs of average scores for various novel enrichment devices:  Baffle Cage With Paper and Treats Overall Average

Figure 3. Graphs of average scores for various novel enrichment devices:  Shake a Treat Overall Averages

Figure 3. Graphs of average scores for various novel enrichment devices:  Paper Burrito Overall Averages


Overall, the enrichment devices utilized during our environmental enrichment project proved to be useful in reducing stereotypical behavior. It was observed that an increase in rotation frequency with the addition of destructible or edible enrichment was more impactful in treating stereotypy than the currently accepted clinical treatment regimen. Shifting from twice-weekly treatment of abnormal behavior with standard enrichment devices to devices that encourage natural behaviors daily and affording all animals within the social group availability to the novel devices, created an environment conducive to correcting unwanted behaviors. The use of dietary enrichment within the novel devices not only gave the animals an opportunity to interact with the devices, but it also supplied them with foraging and extended play with items as they fell from the novel devices. Additionally, dietary enrichment in association with the devices allowed for daily fruit/vegetable/nut dietary needs to be more adequately met/satisfied.


Tyler Bongen, Nick Masterson, Shelby Earley, Kelly Griffey, Matt Day, Crystal Markiewicz, Kathleen Coyle, Madeliene Mottinger, Brandon Gilbertson, Samantha Anderson, Savannah Lundgren, Logan Henz, Haley Frost

No Comments

Post A Comment