By: Andrew R. Halloran, Ph.D., Founder and Lead Consultant, The Elgin Center
Editor’s Note: Andrew R. Halloran, Ph.D., is a primatologist, conservationist, and animal welfare specialist with over 25 years of experience working with chimpanzees in sanctuaries, zoos, and the wild. This is the third in a three-part series by Halloran, first published by the Arcus Foundation, intended to raise awareness about the individuality of chimpanzees and the importance of the complex work done by sanctuaries and rehabilitation centers to care for them. Read Part 1, Burrito’s story, and Read Part 2, Skippy’s story.
At Project Chimps—a large chimpanzee sanctuary in the mountains of north Georgia, U.S.—staff understand that each of their 100+ chimpanzee residents is a unique individual with distinct preferences, needs, and challenges. 19-year-old Leo makes this truth particularly clear.
On a recent day, Leo entered one of his more pronounced episodes of abnormal behavior: zoning out, then slapping his feet, as if he doesn’t understand they are part of his body. While no one knows what triggers Leo’s episodes—maybe a sound, a scent, or a memory—the evidence of his stress is in his actions, and his anxiety escalates into panic.
It is never easy for staff to watch. But they know Leo’s history and what helps him. On this day, staff knew he needed something unique to him: his lifelong companion, Hercules.
For chimpanzees in research labs, a life of deprivation begins early
Leo was born at the New Iberia Research Center in Lafayette, Louisiana, in 2006. Records suggest he was separated from his mother at birth and hand-reared by humans. Just after he turned 1 year old, he was leased to Stony Brook University in New York, along with another chimpanzee named Hercules. They were to be used as test subjects for a study on human bipedalism.
Both chimpanzees were fitted with electrodes into the muscles they used for locomotion and trained to walk bipedally on a treadmill. Scientists used the data as part of research into how humans evolved to walk upright on two legs.
The principal investigator at Stony Brook said that Leo and Hercules were housed in “very large” cages the size of “three moderate-sized bedrooms” with ropes, cardboard boxes, and plastic toys. In reality, according to Project Chimps staff, their world was white concrete walls and chain-link caging—far from what a chimpanzee needs. In the wild, 1-year-old chimpanzees cling to their mother’s back, riding with her as she forages for food. They spend their evenings watching as she makes her night nests high in a forest canopy. They live and learn within large social groups, where they interact with dozens of other chimpanzees on a daily basis. They form bonds, play, interact, and groom.
But Leo and Hercules had none of this. The only thing they had was each other.
While the study was less invasive than many, it required frequent anesthetizations. And more damaging than the surgery and attachment of electrodes was the absence of all that Leo and Hercules had been deprived of: a mother’s care, social bonds, freedom of movement, and the richness of living in the natural world.
During this time, Leo and Hercules became known to the general public. The Nonhuman Rights Project (NhRP), an organization that advocates for legal personhood and rights for nonhuman animals through litigation and education, adopted their cause and began to petition for their relocation to a sanctuary. As the result of NhRP’s work, a judge ordered Stony Brook University to justify their detainment and use in the research project. Six years after their arrival, the university ended its research with Leo and Hercules and sent them back to the New Iberia Research Center.
Despite similar histories, individual chimpanzees express trauma differently
It might seem that two chimpanzees with identical histories would end up in the same shape. However, chimpanzees are complicated, and, as with humans, trauma can affect them differently despite similar experiences.
Back at New Iberia Research Center, Leo and Hercules were not only able to stay together, but also successfully integrated with seven other chimpanzees. Two years later, the group of nine arrived at Project Chimps.
But despite their bonded social group, the complexity of chimpanzee care was clear: There is no one-size-fits-all plan. Leo’s episodes quickly drove this point home to the sanctuary staff. To meet the individual needs of each chimpanzee, care technicians must observe constantly and document each chimp’s unique behaviors and needs—what causes anxiety, what foods are rejected, what enrichment sparks curiosity, what social history shapes trust. Only then can sanctuaries help residents thrive, not just survive.
This is a challenging endeavor in any circumstance. However, it is exponentially more complicated at sanctuaries where chimpanzees come from disparate backgrounds with vastly different histories. Whether the chimp was used in medical or behavioral research, kept alone as a pet or used in entertainment, well-cared-for or abused, assessing what serves a chimp’s well-being is fundamental for sanctuaries to truly fulfill their mission to provide high-quality care for chimpanzees in need.
A lifelong companion: Healing through social bonds
When Hercules arrived at Project Chimps, adjustment came easily. He was highly sociable and interactive—even dominant—with other chimpanzees, soon becoming the leader in the group. But Leo was beset by challenges. He preferred being with staff rather than other chimpanzees, often stayed inside alone, and struggled with episodes of extreme anxiety that included self-directed behaviors like hitting and slapping himself. The staff at Project Chimps worked tirelessly to determine how they could help mitigate Leo’s anxiety and, in turn, abate these episodes.
Over the years, Leo and Hercules continued to acclimate more and more to their new home. And every day, staff worked to provide them exemplary care in support of their welfare and well-being. But even with the best efforts, sometimes chimps have a bad day. On that recent day, that chimp was Leo.
But the staff knew exactly what to do. They acted quickly. A sliding door opened. Hercules entered and embraced Leo, who immediately calmed.
Leo didn’t need medication or human intervention. He needed the touch of his lifelong companion—the one constant solace he has always had. He needed Hercules.
For Leo, sanctuary means more than safety—it means the freedom and space to find healing in the arms of a companion.
