The researchers evaluated 47 Juru\u00e1 red howler monkeys (Alouatta juara) and found green-colored microplastic filaments, smaller than 5 millimeters (0.2 inches), in the stomachs of two individuals. The monkeys, called guaribas or bugios locally, lived in the Mamirau\u00e1 and Aman\u00e3 sustainable development reserves in Amazonas state in northwestern Brazil.<\/p>\n
\u201cThe frequency was low. We found [plastic] in only two monkeys. Still, that\u2019s already a lot. I would have preferred to find none,\u201d lead author Anam\u00e9lia de Souza Jesus, a researcher at the government-funded Mamirau\u00e1 Institute, in Tef\u00e9 in Amazonas state, told Mongabay by phone. \u201cFinding microplastics in preserved environments sounds an alarm. It shows that plastic pollution is reaching places we assumed were protected.\u201d<\/p>\n
No animals were killed or harmed for the study. Rather, the researchers relied on remains of monkeys donated by subsistence hunters through a two-decade partnership between local communities. This allowed the scientists to study organs that would otherwise have been discarded.<\/p>\n
The team collected intact, sealed stomachs from the monkeys and analyzed them in a controlled laboratory environment. The two monkeys that ingested the plastic filaments, visible only when examined under a microscope, were hunted in 2015. <\/p>\n
![\"Plastic](\"https:\/\/www.newsbeep.com\/us\/wp-content\/uploads\/2025\/10\/Screenshot-2025-10-14-at-12-39-52-First-Evidence-of-Microplastic-Ingestion-by-an-Arboreal-Primate-46.png\")
Plastic fiber filaments were found in the stomachs of two Juru\u00e1 red howler monkeys. Image courtesy of Jesus et al. (2025).<\/p>\n
Red howler monkeys spend most of their lives in the forest canopy, eating an herbivorous diet of leaves and fruit. This makes indirect consumption of plastic from other routes, for example, via fish, unlikely, Jesus said. \u00a0<\/p>\n
The v\u00e1rzea forests where the red howler monkeys live are flooded for half of the year. Then, in the dry season, water levels decrease considerably. <\/p>\n
The study\u2019s scientists wrote that they believe contact with plastic may have happened through water from the river or due to plastic waste, such as fishing nets, getting caught higher up in trees as water receded for the dry season. <\/p>\n