Introduction to Environmental Enrichment for Primates

Environmental enrichment refers to items or stimuli that are provided to captive animals to support their behavioral needs. All animals evolved distinct behavioral patterns, and difficulty in engaging in these behaviors can cause frustration or boredom, which, in turn, can lead to stress and the development of abnormal behaviors. Enrichment provides a way to increase opportunities for the expression of species-specific behaviors and decrease the occurrence of abnormal behaviors. As such, environmental enrichment is an integral part of caring for captive animals.

Two of the primary goals of enrichment are to reduce stress and improve the psychological well-being of captive animals. Animals living in captivity are exposed to a variety of stressors in their daily lives. Common husbandry practices, such as cage changes or cleaning, and environmental factors such as lighting, noise and temperature, may cause stress for some individuals. Environmental enrichment can help to ameliorate the effects of potential stressors associated with the captive environment and enhance the animals’ physical and mental health. Furthermore, enrichment can help promote resiliency to stress, which helps animals recover, behaviorally and physiologically, from aversive stimuli. This increased ability to respond appropriately to stress is widely considered an important aspect of well-being in captive animals. 

Enrichment is often classified into five broad and overlapping categories: social, physical, sensory, food, and cognitive/occupational. Ideally, animals should receive enrichment from all categories. Social enrichment typically consists of housing individuals with conspecifics, although it may also include interaction between a nonhuman primate and its caretaker. Positive human-primate interactions can promote psychological well-being for both species.  Social enrichment is described in more detail here. Physical enrichment is a common form of enrichment and includes items designed to provide physical structure (such as perches, floor substrate, or climbing areas) and items that provide opportunities to explore or manipulate (such as toys, mirrors, etc.). Sensory enrichment provides animals with visual, tactile, and olfactory opportunities and includes exposure to various sights (often through television or computer screens), sounds, and smells. Food enrichment provides opportunities for captive animals to increase the amount of time they spend searching for, processing, and eating, behaviors which occupy much of the activity budget of most species in the wild. It includes the use of foraging devices, many of which are commercially available. Finally, cognitive and occupational enrichment provide opportunities for nonhuman primates to obtain physical and/or mental stimulation, and includes both exercise and problem-solving tasks. Animal training can be considered a type of cognitive enrichment because the animals are learning. 

While specifics may change across species, there are general tenets of successful enrichment programs.

a) Be aware of the species’ natural history. Enrichment plans should be customized for the species that is being enriched. Enrichment programs that are appropriate for one species may be inappropriate for another. For example, while owl monkeys (Aotus spp.) utilize nests in the wild, and should be provided with nest boxes in captivity, such nest boxes would be of little value to most macaque species.

b) Enrichment should be goal-oriented. In general, the goal of enrichment is to provide opportunities for animals to increase their time spent in species-typical behaviors and to reduce the amount of time spent in abnormal or undesirable behaviors. Items or approaches that are not achieving appropriate outcomes should be modified or eliminated.

c) Enrichment should do no harm. Safety is an important factor to consider when providing enrichment. Care must be taken to avoid injuries that may occur with various enrichment items. Additionally, in the laboratory setting, it is important to ensure that enrichment does not have untoward effects on experimental outcomes.

d)  Enrichment should be evaluated.  Enrichment offerings should be empirically evaluated to ensure they are meeting their goals. Items that do not have a demonstrable effect upon the well-being of the animals should be reconsidered, and potentially replaced. Enrichment items that are shown to have negative effects (e.g., decreased reproduction, illness), should be eliminated. Even enrichment that has been effectively used for long periods should be regularly evaluated to ensure it is still achieving its desired behavioral goals.

For more information, see the list of websites and workshops, followed by an extensive bibliography on Primate Enrichment.