NABR: New review of long-tailed macaque population recommends two steps for accurate reassessment of long-tailed macaque global population

WASHINGTON, Oct. 28, 2025 /PRNewswire/ -- A recent article published in the American Journal of Primatology criticizes work relied upon by the International Union for Conservation of Nature (IUCN) in its latest determination concerning long-tailed macaque monkeys (Macaca fascicularis).

The article, entitled "Estimating the Abundance of Widely Distributed Primates," concludes that scientific work adopted by the IUCN is "flawed and results in a serious underestimate of the global abundance of the species." The article goes on to state that such population estimates are based upon "a totally unrealistic relationship between habitat suitability and density." The article is available at https://onlinelibrary.wiley.com/doi/full/10.1002/ajp.70082.

The American Journal of Primatology is the official journal of the American Society of Primatologists. The Society's goals are to "promote and encourage the discovery and exchange of information regarding primates."

Long-tailed macaques are used extensively throughout the world in biomedical research given their close approximation to human beings. Five of the 20 most used prescription drugs were developed with the help of long-tailed macaques. Research with long-tailed macaques has been crucial for advances in regenerative medicine, immunology, cancer, vaccine development, and pharmacology, as well as the development of the COVID-19 vaccine. The National Institutes of Health (NIH) recently published a review confirming the importance of long-tailed macaques in conducting biomedical research.

Prior to 2022, long-tailed macaques were designated as "vulnerable" by the IUCN. The IUCN then revised its species designation to "endangered." In 2023, NABR filed a petition challenging the designation of long-tailed macaques, citing improperly used data. After more than two years of deliberation, the IUCN affirmed its status determination, largely ignoring data presented by NABR.

"The latest article published in the American Journal of Primatology confirms that this species is not at risk," said Matthew R. Bailey, president of NABR. "This article also reconfirms that the science underlying the IUCN process is biased, and not reliable," he added.

"Given the importance of long-tailed macaques to ongoing biomedical research throughout the world, it is imperative that the U.S. and other countries conduct a more objective assessment of the species' status before further actions are taken."

About the National Association for Biomedical Research
Founded in 1979, NABR is the only 501(c)(6) non-profit association dedicated to sound public policy for the humane use of animals in biomedical research, education, and testing. Members include more than 340 universities, medical and veterinary schools, teaching hospitals, pharmaceutical and biotechnology companies, patient groups, and academic and professional societies who rely on humane and responsible animal research to advance global human and animal health. Learn more about us at www.nabr.org.

Contact: Eva Maciejewski
emaciejewski@nabr.org
(202) 967-8305

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