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University of Wisconsin–Madison
Wisconsin National Primate Research Center
A legacy of life-saving research and humane animal care

WNPRC Behavioral Services Unit provides science-based enrichment for nonhuman primates

Three common marmosets at the center perching on a branch, with hammocks overhead.

In addition to the WNPRC lobby marmosets, often viewed by the public on the Callicam, another 230 common marmosets, such as these, are part of the center’s colony.

By Jessica Knackert, editorial intern
with center photos by WNPRC Animal Services staff
Feb. 28, 2020

In the front lobby of the Wisconsin National Primate Research Center (WNPRC), visitors can observe a family of marmosets living together. Their area is filled with a variety of items to play and interact with, such as a long yellow hammock shaped like a banana and large branches from trees native to the state of Wisconsin. But who decides that these are the best things to include in a marmoset habitat?

Over the years, animal research methods have evolved dramatically. Animal welfare and species-specific care are always crucial components to consider, especially with nonhuman primate models. At the WNPRC, the Behavioral Services Unit (BSU) in the Animal Services Division focuses specifically on these goals by ensuring that all three species of primates housed by the center receive the best care possible.

The head of the Behavioral Services Unit is Peter Pierre, Ph.D., associate scientist. Pierre began his position back in July 2011. Prior to his involvement at the WNPRC, he worked as a scientist for Wake Forest School of Medicine in Winston-Salem, North Carolina, where he studied biobehavioral development in a number of different primate species.

With his past research and his ongoing position at the WNPRC, Pierre has accumulated 20 years working with nonhuman primates. His research has spanned a variety of topics, from cognitive and motor testing to pharmacological and neuroimaging studies to even analyzing the difference in stress reactivity between individuals. His expertise in these areas has helped lead the BSU into a new era of enrichment and care practices.

The addition of Pierre came at an ideal time for the center. Before he was appointed, the unit had already been moving toward an approach to behavioral management that was more evidence-based. Pierre’s scientific background as well as his experience in behavioral research with nonhuman primates made him the perfect candidate to continue this transition.

Today, as BSU director, Pierre outlines four main goals that the center strives to achieve.

“Our first goal focuses on proper socialization,” Pierre said. “Primates are social creatures, and the strategies applied for each species should also fit with the needs of each individual.” For example, he explained, marmosets at the WNPRC are housed as a family unit based on their need for high levels of socialization and their reliance on alloparenting, a behavior that requires all members of the family to care for offspring. The BSU is also constantly adapting and improving on techniques to optimize socialization. Most recently, plans are in place to expand social housing to offer greater space to rhesus macaques who often live in pairs at the center once they reach adulthood.

The unit also focuses on taking an evidence-based approach to provide enrichment that ensures animal health and well-being. This enrichment works to promote species-typical behavior and prolonged engagement for nonhuman primates.

Brittany Peterson, a behavioral technician who works with Pierre at the WNPRC, presented her work on enrichment devices at the annual American Society of Primatologists meeting this past August at the University of Wisconsin-Madison. Her study involved eight male rhesus macaques. She measured their use of seven different toys commonly used at the center that promote foraging behavior in order to simulate strategies used by rhesus in the wild.

Brittany Peterson, left, presents her poster on foraging toys for laboratory rhesus monkeys at the American Society of Primatologists meeting in Madison last August. (J. Lenon photo)

Brittany Peterson, left, presents her poster on foraging toys for laboratory rhesus macaques at the American Society of Primatologists meeting in Madison last August. (J. Lenon photo)

The study differed from past evaluations of enrichment devices in that it applied the use of an actimeter, a device previously used by Pierre to measure the motion of individual primates. Peterson described the device as “a little Fitbit” attached to each toy to record movement.

“The big issue with assessing enrichment devices up to this point was that it was so tedious,” she pointed out. Previous methods have required scientists to sit and observe in person or to go through hours of video to record whether an individual touched a device or not. This form of data collection was not always the most reliable and it took up a lot of time. Applying actimeters makes the process much quicker. The data collected by the device can be easily transferred to a statistical analysis program. It also increases reliability by eliminating human bias and removing the observer effect that can result when humans are present in the same room as an animal, causing them to act outside of their typical behavior.

The data collected from the study revealed that the suet feeder, a box-shaped toy formed by metal wiring to allow primates to reach inside for food, came out on top as having the highest average interaction. In addition, Peterson highlighted that the BSU staff not only wants to promote high engagement, but also prolonged interaction. The hour-long trial was broken down into 20-minute sections to measure how interaction with each device progressed over time. While the suet feeder showed the highest levels of initial movement, interaction with the device saw a dramatic decline after the first 20 minutes of use. As Peterson explained, this most likely indicates the individual had been able to remove all of the food from the device and no longer had any reason to interact with it. Some devices, however, did show greater potential in this arena. Peterson specifically highlighted the promise displayed by the turf tube, a plastic cylinder covered with artificial turf. It didn’t start at the highest level of interaction, but engagement with it remained fairly steady over the entire hour compared to the other devices. It was also the only device to still have food remaining in it once the trial was over.

A suet feeder for rhesus macaques at the WNPRC.

Suet feeders filled with fresh fruit for rhesus macaques at the WNPRC.

Rhesus monkeys at the center engaged in foraging behaviors with enrichment devices at the WNPRC.

Rhesus monkeys engaged in foraging behaviors with enrichment devices at the WNPRC.

With marmosets, the researchers have found that, while in the past, caretakers have given marmosets miniaturized versions of toys given to macaques, the marmosets do not tend to manipulate objects with their hands in the same way as macaques. Marmosets are more into biting and gouging. “Furthermore,” Pierre said, “We found that the marmosets will gouge a stationary device, such as a tree branch or other anchored wooden object, but not a moveable one, such as a hanging object.” Findings like these highlight the need to consider how interactive opportunities fit with how each animal will engage with toys, devices or objects of interest.

Applying research and novel approaches such as this have been instrumental to the success of the WNPRC’s animal programs. “With any enrichment program, you want to be constantly critiquing, assessing, and improving it to make it better and to make sure that the types of enrichment you’re providing for your animals are improving their well-being,” emphasized Peterson. She also highlighted how important the support and wide range of expertise from Pierre was to the success of the project. “He wears a lot of hats,” she stated.

Outside of promoting species-typical behavior, Pierre states that the BSU also strives to increase surveillance of atypical behavior among its nonhuman primates. Unit staff record daily observations of the animals under their care. They share this information with scientists, veterinarians, and colony management staff who then use it to identify an occasional individual that may need to be treated or assessed for further intervention. This type of monitoring has allowed staff to diagnose and treat individuals more efficiently over the past decade.

The final ideal that Pierre and the BSU work to uphold is habituating all animals housed at the center to care and research procedures. This not only ensures the safety of the animals, but of the people who work with and care for them daily. Pierre describes that more time is being dedicated to training animals to be comfortable with care and research procedures. The BSU also focuses on campus-wide training for nonhuman primate staff to ensure that all animals housed at the center receive the most up-to-date, evidence-based care and treatment.

Pierre’s influence at the WNPRC has not only served to improve the care and health of its animals, but of all nonhuman primates housed in research facilities across the nation. He also uses his experience to support young scientists, like Peterson, while promoting the best methods available when conducting animal research. His work shows how important an evidence-based approach is to refining the methods used to enhance the care and welfare of nonhuman primates.

In addition to Pierre and co-principal investigator David Abbott, the BSU staff includes Jennifer Sullivan, behavioral services coordinator, and behavioral technicians Brittany Peterson, Michele Rosga, and Tammy Aird. In addition, UW–Madison students contribute to the BSU by pursuing evidence-based projects focused on enhancing animal welfare by stimulating environments that invite the expression of species-typical behavior.  As participants in these projects, student researchers acquire skills in observing animal behavior, experimental design, method development, and analysis.

Enrichment toys and food for rhesus macaques at the WNPRC.

Enrichment toys, chow and snacks for rhesus macaques at the WNPRC.

Selected References

Dutton MB, Pierre PJ, Bailoo JD, Warkins E, Michel GF, Bennett AJ. A model quantitative assessment tool for nonhuman primate environmental enrichment plansbioRxiv 341206. June 8, 2018.

Bennett AJ, Bailoo JD, Dutton M, Michel GF, Pierre PJ. PsyArXiv. Psychological science applied to improve captive animal care: A model for development of a systematic, evidence-based assessment of environmental enrichment for nonhuman primates. June 7, 2018.

Baker, KC, Bloomsmith MA, Coleman K, Crockett CM, Fahey M, Lutz C, McCowan B. Pierre PJ, Weed J, Worlein J. The Behavioral Management Consortium: A partnership for promoting consensus and best practices. The Handbook of Nonhuman Primate Management. Stephen Schapiro (Eds). John Wiley & Sons, Inc. 2017.

Bennett AJ, Perkins CM, Tenpas PD, Reinebach AL, Pierre PJ. Moving evidence into practice: cost analysis and assessment of macaques’ sustained behavioral engagement with videogames and foraging devices. Am J Primatol. 2016 Dec;78(12):1250-1264.

Rosga M, Pierre PJ. 2013. Incorporating transfer training as a daily husbandry routine for pen-housed monkeys. Lab Animal Science Professional, March, pp 36-38.