Scientists have detected microplastics in the digestive systems of red howler monkeys living in protected areas in the Brazilian Amazon, marking the first evidence of plastic ingestion by a tree-dwelling primate, according to a recent study.
The researchers evaluated 47 Juruá 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 Mamirauá and Amanã sustainable development reserves in Amazonas state in northwestern Brazil.
“The frequency was low. We found [plastic] in only two monkeys. Still, that’s already a lot. I would have preferred to find none,” lead author Anamélia de Souza Jesus, a researcher at the government-funded Mamirauá Institute, in Tefé in Amazonas state, told Mongabay by phone. “Finding microplastics in preserved environments sounds an alarm. It shows that plastic pollution is reaching places we assumed were protected.”
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.
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.
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.
The várzea forests where the red howler monkeys live are flooded for half of the year. Then, in the dry season, water levels decrease considerably.
The study’s 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.
A previous review of plastic pollution in the Amazon, also conducted by the Mamirauá Institute, found plastic contamination in fish, turtles, manatees and birds, as well as in river water and soil sediments. But evidence of microplastics reaching tree-dwelling monkeys had never been documented before, until now.
“We now have evidence that [plastic waste] is reaching places that we thought would be inaccessible,” Jesus said. “We can try and reach the people who can implement better waste management, here in Tefé and across the basin.”
Banner image: Juruá red howler monkeys. Image courtesy of Anamélia de Souza Jesus.
Credits
