Environmental Enrichment

The Behavioral Management Program oversees environmental enrichment of laboratory monkeys at the Washington National Primate Research Center (WaNPRC)

For monkeys at the WaNPRC, environmental enrichment is a part of daily life. Environmental enrichment has been shown to improve the psychological health of nonhuman primates. Attention to the psychological well-being of laboratory primates derives from ethical concerns for the welfare of our fellow creatures and from a need to ensure healthy subjects for research. The 1985 amendment to the 1966 Animal Welfare Act introduced the concept of psychological well-being into Federal law. It led to the U. S. Department of Agriculture’s 1991 Animal Welfare Standards requiring research institutions, zoos, and other facilities with captive nonhuman primates to formulate Environmental Enhancement Plans to enrich the primates’ physical environment and address their social needs. Although the USDA provides guidelines as to the necessary content of the Environmental Enhancement Plan each institution develops its own plan.

The University of Washington’s Environmental Enhancement Plan was developed by WaNPRC Behavioral Management staff and the Attending Veterinarian of the University of Washington and was approved by the UW Institutional Animal Care and Use Committee (IACUC). This plan is revised yearly to ensure that enrichment strategies are maintained in alignment with current professional standards. Every primate housed at the WaNPRC participates in the Environmental Enhancement Plan, as required by Federal law. On a day-to-day basis, environmental enrichment is administered by psychological well-being coordinators and animal husbandry staff.

The WaNPRC Environmental Enhancement Plan includes several types of enrichment. Explore some of them in the following categories.

Social Housing:

group-housingThe importance of social housing has been emphasized in the Guide for The Care and Use of Laboratory Animals. Animal welfare regulations, guidelines and published research studies concur that social housing of nonhuman primates improves their psychological well-being. In the wild, all species of nonhuman primates housed at the WaNPRC typically live in social groups. In these groups they form intricate relationships, and they spend a great deal of time engaged in social behaviors. In captivity, social contact provides the opportunity for animals to express these species-typical behaviors including social grooming and play. It should be noted that in a captive setting, some species-typical behaviors which occur in the wild should be managed so as to minimize their expression (e.g., aggression), or restricted to certain individuals (e.g., mating).

It is the policy of the WaNPRC that all NHPs that are not exempted from social contact be housed socially and that WaNPRC staff will ensure compliance with the spirit of these guidelines. Social housing includes two or more animals housed in a compound, a large cage or in run-through connected cages. Exemptions from social contact may be granted for veterinary concerns or for IACUC approved scientific reasons. Animals who must be exempted from social housing receive extra nonsocial environmental enrichment. Also, whenever possible, these animals will receive a periodic rotation through large exercise cages or intermittent or protected social contact.

Food Treats and Foraging Experiences:

Food treats and foraging experiences enhance the psychological well-being of laboratory monkeys in various ways. They stimulate varied taste experiences, encourage different manipulative and foraging behaviors, vary the daily routine, and provide positive social contact with the human caregiver who delivers them. They also offer a variety of food types resembling the annual diversity found in the wild. Macaques and baboons in the wild may eat more than 100 different kinds of foods during a year.

The Behavior Management Program takes pride in the variety of food treats and foraging items provided to the monkeys. In accordance with guidelines provided by the USDA, we distinguish between a simple food treat and a foraging experience. A food treat is any edible item providing variety from dry biscuit diet and given in a small amount. A produce food treat is a fresh fruit or vegetable treat. More than 60 different kinds have been given to the monkeys, from Apples to Zucchinis. Non-produce food treats include cereals, nuts, dried fruits, dried pasta and more.

A foraging experience is any food or drink enrichment that requires extra manipulation and prolongs consumption time, thus providing mental stimulation. Examples include:

PuzzleBall_Edit Puzzle Ball – Peanuts or cereal put in a foraging device, such as the Puzzle Ball developed at WaNPRC. The Puzzle Ball Loader protects staff while provisioning the puzzle ball.
TreatCups_edit Treat Cups – Frozen items such as produce pieces, juice, and dry treats frozen in Kong toys, in paper cups, in egg cartons, in ice-cube trays, or in tortillas. View the Catarrine Café Cookbook for some great recipes.
Pigtail-pumpkin_Edit Complex Foods – Certain whole fruits and vegetables, such as the donated pumpkins provided every Halloween. Whole coconuts and hard-boiled eggs (in the shell) also fall into this category.
ForagingTubes_edit Foraging Tube – Paper and food combinations such as the “foraging tube,” a WaNPRC Behavior Management program invention. It is made from a paper towel roll, encrusted with peanut butter, oatmeal, and raisins, or other items, and hung outside of the cage on a metal tube “roller bar.”

Food and foraging treats are generally given in small amounts (less than 5% of total caloric intake) so that they don’t disrupt the animal’s digestion or cause excess weight gain.

WaNPRC Behavioral Management Staff has developed a cookbook of foraging treats “The Catarrhine Café Cookbook.” You can download a free copy of this cookbook by clicking here.

Animals are also occasionally given other types of non-food foraging items such as paper and wood.


In the wild, nonhuman primates spend a great deal of time manipulating their environment. At the WaNPRC, we provide monkeys with a wide variety of cage toys to encourage environmental manipulation. Each monkey is provided with at least one toy which is changed out often to maintain the monkey’s interest. These toys are usually some type of very durable dog toy. The Behavioral Management Program carefully evaluates new toys before widespread adoption because some are unsafe for monkeys or wear out too quickly to be cost effective. We also want to choose those toys that engage the animal’s attention for the longest period of time.


To address their arboreal nature, we provide laboratory monkeys access to a place to sit or climb above floor level. Individual cages have perches that a monkey can sit or lie upon, or use for climbing up and down. Monkeys in group compounds use climbing structures made from recycled caging and plastic barrels. Infants that must be raised in the nursery have a cloth-covered swinging device upon which they can cling and perch.