A state of psychological well-being means that an animal's physical and emotional needs are met. Because nonhuman primates are curious and social creatures, their psychological health is critical in all environments, whether a research setting, zoo, or private ownership.
Factors affecting the psychological health of nonhuman primates include socialization with conspecifics, opportunities to engage in species-specific behaviors such as foraging and environmental exploration, and appropriate housing that enables and encourages species-typical movements and postures.
All five senses (sight, smell, taste, hearing, touch) should be taken into consideration when designing an enrichment program for nonhuman primates.
Socialization should be the first consideration for any program targeting the psychological well-being of primates, whether it is with compatible animals of the same or similar species, with human caretakers, or via other compatible social outlets. Socialization can include auditory, visual, or physical contact, depending on the individual primate's needs.
Positive reinforcement of desired behaviors provides substantial benefit to most nonhuman primate species during interactions with veterinarians and should be provided, when practical, within the constraints of research protocols and daily management practices. Individual nonhuman primates can be trained to present limbs or station in a certain location for clinical care, and training interactions can decrease the stress associated with handling and improve the bond between caretaker and nonhuman primate.
For hospitalized nonhuman primates requiring treatment away from their normal social housing, video calls with their home group or relatives might enable continued affiliative behaviors during treatment and recovery.
When enclosures for nonhuman primates are designed, sanitation needs within resting, play, and foraging areas should be considered. Thermoneutral perching materials, such as cloth or polymerized plastics, should be considered, especially for smaller species. Limbs, ropes, and climbing areas should be provided for brachiating (swinging by the arms) species.
Visual barriers of varying sizes and materials provide nonhuman primates opportunities for rest and seclusion. For New World primate species, nesting boxes should be provided to enable normal resting/hiding behaviors. When enclosures are of the minimum legal size, in light of nonhuman primates' normal range and movement both arboreally and on the ground, increasing vertical space might provide opportunity for improved social behaviors with conspecifics, exploration, and exercise.
The animal's life stage should also be considered, because young or very old animals might require altered environments to ensure safety and mobility within the enclosure.
Enrichment for nonhuman primates should take into account the encouragement of species-typical behaviors. Ethogram data from primates in a natural setting can inform the type of enrichment to provide. Enrichment might include foraging boards or other food-related enrichment, manipulable mirrors, and a variety of cage toys provided on a rotating schedule to maintain novelty (see water enrichment and drum enrichment videos).
Creative application of safe, destructible enrichment items, such as nontoxic cardboard boxes or papier-mâché piñatas, might increase the amount of time that primates interact with a new toy or food item. Radios, water features, scented toys, or diffusers can provide additional auditory and olfactory enrichment.
Periodic (at least semiannual) behavioral assessments and reviews of the effectiveness of all components of the enrichment program should be performed by appropriately trained individuals on a routine basis.
If observed, stereotypical or self-injurious behaviors should be addressed. In nonhuman primates, repetitive behaviors such as pacing, flipping, limb floating, hair plucking, and overgrooming the extremities often result from stress and inadequate stimulation. Improvements in husbandry and socialization should be addressed first, followed by behavioral redirection or pharmacological intervention.
Regular reassessments are recommended to ensure resolution of concerning behaviors in nonhuman primates. Any discomfort associated with pain should be addressed with an appropriate analgesic regimen, such as gabapentin (10–20 mg/kg, PO, every 8–12 hours as needed) or NSAIDs such as meloxicam (0.2 mg/kg, PO, once, followed by 0.1 mg/kg, PO or SC, every 24 hours as needed).
Chronic medications should address the anxiety or stress component of the nonhuman primate's condition. Fluoxetine (0.2 mg/kg, PO, every 24 hours, increased as needed) can be used as a selective serotonin reuptake inhibitor (SSRI), but the beneficial effects might take 4–6 weeks to be clear. In acute cases, fluoxetine can be used in conjunction with a benzodiazepine such as diazepam (0.5–1 mg/kg, PO, IV, or IM, every 8–12 hours as needed).
Addressing and ameliorating preexisting abnormal behaviors in nonhuman primates is important and might take several months. When SSRIs such as fluoxetine are discontinued, the patient should be slowly weaned off the medication rather than abruptly stopped.
Key Points
Socialization with conspecifics is key to the psychological well-being of nonhuman primates.
When SSRIs such as fluoxetine are discontinued, the patient should be slowly weaned off the medication rather than abruptly stopped.
For More Information
National Institutes of Health, Office of Laboratory Animal Welfare, Enrichment and Social Housing Resources
Lutz CK, Novak MA. Environmental enrichment for nonhuman primates: theory and application. ILAR J. 2005;46(2):178-191.
Tobey E, Adams K. Environmental Enrichments for Nonhuman Primates: A Resource Guide. Animal Welfare Information Center, National Agricultural Library; 2021.
