"Ramadewa looked at the numerous troops of monkeys. They were at ease and happy and showed their liveliness. All their movements, their noisy voices, their way of sleeping on branches made him happy just to look at them." —Verse 151:V1, Kakawin Ramayana

I saw macaques for the first time along the river's edge on the island of Borneo in 1983. I was in a boat with scientist and conservationist Dr. Biruté Galdikas on our way to the orangutan rehabilitation and research site she established on the island. I was 17, had never traveled outside the United States, and knew nothing about primates. Dr. Galdikas, who celebrated her 50th anniversary of orangutan fieldwork and conservation in 2021, took a chance on me.

I spent my first few weeks learning how to move around in Borneo's tropical rainforest, trying to keep up with the orangutans, who are big, brilliant, and brightly colored apes. They are extraordinary, and taking your eyes off them is hard. Nevertheless, my attention often wandered to another of the reserve's primates—the troop of long-tailed macaques (Macaca fascicularis). These slender monkeys with variegated green fur and striking facial hair bounded on all fours through the trees, with their long, slim tails acting as a counterbalance.

Keystone Role in Ecosystems

Macaques are seed dispersers, predators, and prey, making them a keystone species in the edge environments they occupy; remove them from the forest, and you risk a cascade of ecological consequences. I could reliably find them within half a mile of the river's edge, where they spent their days foraging, grooming, swimming, and sleeping. They also routinely wandered into our camp, easily navigating the "edges" we had opened in the forest. The adults were fiercely protective of the infants and juveniles. The troop gathered at a large sleeping tree along the river each evening before dark. When everyone was accounted for in this troop of 30 highly social and intelligent macaques, the members would huddle together for warmth, safety, and companionship.

The months I spent in Borneo collecting observational data on macaques eventually led me into an academic and research career. Throughout this time, I focused on how infectious diseases move between human and macaque populations and the consequences for primate conservation and public health.

Members of the genus Macaca, with their unsurpassed ability to inhabit the edges that humans create when we alter the environment, are the most geographically diverse and successful nonhuman primate group in the world. Multiple species of macaques are naturally distributed throughout Asia. Macaques have also successfully colonized Mauritius and Florida, while North Africa is home to a single species known as Barbary macaques.

Exploitation for Biomedical Research

The primate biomedical research community has relentlessly targeted three species of macaques: long-tailed, rhesus, and pigtailed. Ironically, macaques' remarkable ecological and behavioral adaptability has increased their visibility, ultimately putting their lives at risk. Countries like the U.S. are increasingly using them in experiments to advance human health.

However, primates caught up in the experimentation pipeline have consistently proven to be poor models for human health research. One reason for this is that their biology differs significantly from ours. Furthermore, the presence of unintended and/or undetected pathogens and the immune-crushing stress of captivity distort results, making data unreliable. Decades of primate research have failed to deliver meaningful advancements for human health, while modern, human-relevant methods are proving far more effective and ethical.

According to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) database, more than 1.5 million long-tailed, rhesus, and pigtailed macaques have been exported from Asia and Mauritius to laboratories around the world since 1975. In 2022, the International Union for the Conservation of Nature Red List of Threatened Species elevated long-tailed and pig-tailed macaques to Endangered.

The Cruelty of Capture and Transport

These monkeys have been relentlessly trapped in urban and semi-urban areas. They have been grabbed as their sleeping trees were cut down and netted as they tried to swim away. Entire troops have been captured after being isolated in the one tree that remained in a crop field. Untold numbers of adult macaques have been beaten to death as they tried desperately to hold onto their infants or protect their friends while they were being captured to be used for experimentation. More deaths followed as they were stuffed into rice sacks, wire bags, or wooden boxes after they were captured.

The 1.5 million exported macaques were the "survivors" of these ordeals. The actual number of macaques extracted from Asia and Mauritius is much larger; captive-born and wild-born macaques form the "breeding stock" of the "monkey farms" in Asia and Mauritius. The stress of capture, the horrific conditions in which the macaques are kept, and their exposure to pathogens while in captivity have led many of them to die from disease. These monkeys are then "replaced" with more wild-caught macaques.

In January 2022, a truck transporting over a hundred macaques crashed in Danville, Pennsylvania. The macaques had traveled nearly 10,000 miles from Mauritius. Images of the cramped, airless wooden crates used for transport have exposed this industry's cruelty, secrecy, greed, and danger. The crash was so violent that some crates burst open, and three monkeys escaped into the surrounding area. Representatives from the Centers for Disease Control and Prevention (CDC) did a risk assessment and decided that the three escaped macaques be shot on sight.

News coverage of the situation spread around the world. People wanted to know where the monkeys had come from, where they were going, if they carried diseases, and if there was anything to fear. The CDC's lack of transparency about the status of the surviving monkeys or even the location of the CDC-approved quarantine facility to which they were headed is disturbing.

The CDC reports that between 2013 and 2023, more than 285,000 macaques were imported into the U.S. These monkeys arrived by plane in hundreds of shipments. From the port of entry, they were loaded into trucks and sent to the approved quarantine sites for a mandatory 31 days of isolation, testing, and observation.

Public Health Risks

Before 1975, there was no federally mandated quarantine program for imported primates despite the arrival of primates infected with viral hemorrhagic fevers, tuberculosis, deadly diarrheal diseases, fatal diseases transmitted by mosquitoes, and herpes B—a zoonotic macaque virus. However, the CDC's mandated quarantine, which has not changed significantly over the past decades, still only requires that imported primates be screened for tuberculosis and "monitored for signs of illness that could represent a zoonotic disease (a disease that can spread from animals to humans)."

Not all the monkeys make it out of quarantine alive, and tuberculosis infections that the CDC screens for are often missed and show up months or years later, threatening public health and further undermining the utility of these monkeys as biomedical models. Post-quarantine, the surviving monkeys are dispersed to commercial facilities and laboratories around the country, all too often still infected with diverse strains of tuberculosis or deadly bacterial pathogens that the CDC admits cannot be detected with its established protocols.

Certificates of veterinary inspection (CVIs) that PETA obtained from agriculture departments in numerous states give a further glimpse into the extent of monkey transport across the U.S. CVIs are required by the U.S. Department of Agriculture when monkeys are transported across state lines. PETA has pieced together a monkey transport map. Each line represents the journey the monkeys made between the lab, breeder, or importer that sold them and the facility that purchased them. PETA has yet to uncover more routes, many of which have been used multiple times since 2018.

Pause for a moment and consider the magnitude and cost of this monkey madness: The next disaster like the one that happened in Danville, Pennsylvania, in which a truck crashed while transporting monkeys could happen in your community. No one is safe—the monkeys are on the move even before they arrive in the U.S. Separated from their family and friends packed into small wooden crates, they are terrified, cold, and hungry. Some die in transit as they are moved by trucks and planes across the globe. In these vulnerable and stressed conditions, they are likely immunocompromised, increasing the risk that they will shed pathogens that can cause human diseases. Even the experimenters have acknowledged that the large colony of monkeys at their facilities—in places such as Texas, Florida, Louisiana, Georgia, North Carolina, and California—threaten public health.

Legal and Ethical Challenges

In late 2022, the United States Fish and Wildlife Service and the Department of Justice unveiled indictments stemming from a five-year undercover investigation in Cambodia. The operation uncovered a large-scale international scheme in which tens of thousands of wild-caught long-tailed macaques were illegally smuggled into the United States under the guise of being captive-bred.

This "monkey-laundering" operation not only violated wildlife trafficking laws but also exposed the grave consequences of such illegal trade and the billion-dollar industry backing it. The capture and trafficking of wild monkeys inflicts horrific suffering on the animals, threatens wild populations with extinction, and compromises scientific research by introducing undocumented and potentially sick animals into the primate experimentation pipeline.

Macaques are ostensibly being rounded up from forests and urban areas to provide us with lifesaving treatments and vaccines. But it doesn't work that way—macaques aren't furry little humans with long tails. Their immune systems and biology are very different from ours. Despite decades of promises and hundreds of thousands of dead monkeys, experiments using monkeys have not resulted in effective vaccines for HIV, tuberculosis, malaria, or other dreaded human diseases. COVID-19 experiments have shown the scientific community how irrelevant and often misleading monkey studies are.

Between 2008 and 2019, more than 700,000 "specimens" (i.e., blood, tissue, and body parts) from an unknown number of long-tailed macaques were exported from Asia—this is in addition to the 450,000 live long-tailed macaques who were shipped out for use in biomedical experiments. A study published in February 2022 concluded that the extraction of macaques from Asia for use in biomedical research is a multibillion-dollar industry.

A Call for Change

However, progress has been made in the right direction. As of March 2023, the U.S. Fish and Wildlife Service (FWS) has halted the importation of monkeys from Cambodia captured from the wild for U.S. laboratories. Imports are effectively suspended for up to two years, as the FWS now requires a DNA test—yet to be developed—to prove that monkeys were bred in captivity, ensuring protection for these animals in the meantime. Still, this is a small victory, and much more remains to be done.

Macaques are extraordinarily resilient animals, but we're pushing them over the edge. Experimenting on them is cruel and leads to unnecessary suffering and death. Our abuse of these animals needs to end.

Lisa Jones-Engel, PhD, is a primate scientist and a Fulbright scholar. She has been studying primates for more than four decades, and her scientific career has spanned the field, the research laboratory, and the undergraduate classroom. Jones-Engel is the senior science adviser on primate experimentation with PETA's Laboratory Investigations Department.

This article was produced by Earth | Food | Life, a project of the Independent Media Institute.