Improper Primate Release Fuels Interspecific Mating: Cases of Two Mixed-Species Groups in Bangladesh

Wildlife trafficking has escalated in recent years, leading to a rise in animal rescues every year. In Bangladesh, increasing numbers of primates are being rescued from illegal trades and private collections. Often, these confiscated individuals are released into the wild without proper assessment and rigorous planning. The survivability of these animals, as well as the potential negative impacts on both the released individual and recipient ecosystems, has not been systematically evaluated. In this study, we document two cases of misguided primate releases outside their natural ranges with potentially significant consequences. At two sites, two released individuals, an Assamese macaque (Macaca assamensis) and a capped langur (Trachypithecus pileatus), integrated into groups of native primates and engaged in interspecific mating. Community interviews further indicated another improper release of an Assamese macaque at another site. These incidents likely resulted from species misidentification and raise serious concerns regarding mixed-species associations and potential hybridization between native and non-native primates. Collectively, our findings underscore the need for rigorous species-level verification prior to releases, adherence to IUCN translocation guidelines, and development of national protocols to mitigate human-mediated hybridization risks and to safeguard native biodiversity.