Presence and Hazard Assessment of Microplastics in Mexican Howler Monkeys (Alouatta palliata ssp. mexicana) of the Los Tuxtlas Biosphere Reserve, Mexico

Abstract

• First study following established methods for the report of microplastics in wild American non-human primates. • Results show that even natural protected areas face plastic contamination. • Fecal samples are a non-invasive way to assess microplastic pollution in wild primates. • More studies on terrestrial mammals are urgently needed to protect endangered species. Microplastic pollution is an emerging conservation threat to wildlife in both terrestrial and aquatic habitats. However, little is known about its presence in terrestrial ecosystems. How microplastics threaten non-human primates remains poorly understood, and to our knowledge, no study following established methods has been conducted on the American continent. Therefore, this study aimed to detect the presence of microplastics in the feces of the endangered Mexican howler monkey ( Alouatta palliata mexicana ) from the Los Tuxtlas Biosphere Reserve, Veracruz, Mexico. We analyzed 66 fecal samples and found that more than 90% contained microplastics confirmed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), with a mean abundance of 1.49 ± 1.63 particles/g dry weight (DW). The Polymer Hazard Index (PHI) for the polymer detected in fecal samples was calculated, and of the 31 polymer types identified, 12 fell into one of the hazard categories. PHI values ranged from 0.01 to 401.22 and were classified into hazard levels I to IV. These findings emphasize the urgent need for information on the presence and potential consequences of microplastic exposure in endangered terrestrial species.