Enriching Macaque Living Conditions

Story and photos by Jennifer Green, Research Assistant
Queen's University of Kingston, Ontario

I work to promote the well-being of three adult male rhesus macaques who live together in a pen-like enclosure ("Use of Enclosures with Functional Vertical Space by Captive Rhesus Monkeys Involved in Biomedical Research," Journal of the American Association for Laboratory Animal Science. Clarerence WM, Scott JP, Dorris MC, Pare M 2006). They are involved in biomedical research and must be removed from the enclosure for approximately three hours per day. In the wild, macaques spend a great deal of their days searching for, retrieving and processing food. Therefore, it is not surprising that the easiest way to provide enrichment for the captive animals involves food. Making it more difficult for them to access their food promotes foraging behavior.

I have come up with several novel feeding enrichment items (see column at left). However, preparing them can be time-consuming and is not feasible on a daily basis. Fortunately, there are other easy, cost-effective and interesting options. In our laboratory, students and staff bring in plastic bottles, cardboard boxes and paper rolls. These items are used to encourage our monkeys to work for their food, instead of having it distributed in freely accessible food hoppers.

For example, one of my primate's favorite vegetable is sweet potatoes or yams. Instead of just handing him a yam after he has completed his work for the day, I cut it into small pieces that I stuff into bottles or hide in a box filled with recycled paper. When he returns to his cage, I give him the treat. He then spends the next 20 minutes or longer getting all the yam pieces and eating them.

Using food enrichment is not the only way our lab tries to improve the living conditions for research primates. We strive to increase normal behaviors and activity levels by keeping our animals in a large enclosure furnished with high perches located above human eye level, as well as substrate bedding on the floor to encourage additional foraging behavior. Perches, logs, PVC swings and milk crates allow the primates to move around the enclosures, accessing various views at different levels.

Non-breakable acrylic mirrors amuse our monkeys more than any other objects. We mount some mirrors on the walls so animals can view all areas in the room and outside in the hallways. We also hand them small pieces of this non-breakable mirror material, which they carry around and use to check every angle in the enclosure. They often use the mirrors to look at another cage mate—or at me—without being noticed.

The benefits of providing macaques in research labs interesting living conditions can be seen in many areas. Less boredom and frustration reduces distress and therefore increases the validity of research data collected from the animals. It is our goal to continue to seek novel and interesting ways to promote the behavioral well-being of our animals. They are making the ultimate sacrifice for our benefit, and we must keep them as well and content as possible.

Feeding Enrichment

Frozen Frisbee Salads: Plastic frisbees are layered with fruit and veggies, covered in water or juice, and frozen overnight. These can be handed directly to the primates or hung outside of the cages. The animals seem to have a great time picking up the treats as they gradually thaw.

Pylon Surprises: Plastic children's street cones containing small dry treats such as dried peas, raisins, seeds or nuts are zip tied together with holes on each end. The animals must manipulate the pylons to access the treats.

Foraging Crates: Plastic milk crates are filled with magazine paper wrapped around dry treats. Primates must manipulate the paper to find treats, some of which will fall out on the cage floor and create an additional foraging opportunity.

Twine Cones: Pinecones rolled in a sticky substance such as jam, honey or peanut butter and covered with a mixture of seeds and nuts are hung with braided twine outside of the cages. The monkeys must pick at seeds and nuts through the mesh of the cage wall and maneuver the twine to retrieve the treats.

Mop Medleys: Mop heads strung with pasta and dried treats are hung on the outside of the cages. The animals have to remove the treats from the mop strings through the mesh of the cage walls.