New research from the German Primate Center — Leibniz Institute for Primate Research — highlights a serious issue for two endangered primate species in Bangladesh: Phayre’s langurs (Trachypithecus phayrei) and capped langurs (Trachypithecus pileatus). In mixed groups of these species, hybrids have been discovered and confirmed through genetic testing. If hybridization persists, it threatens the existence of one or both species (International Journal of Primatology).
During a five-year period (2018-2023), an international team of researchers, led by Tanvir Ahmed, a PhD candidate at the German Primate Center, examined langur populations in northeastern Bangladesh. They identified that 8 out of 98 studied langur groups included both Phayre’s and capped langurs, with three groups showing individuals that were hybrids of the two species. Genetic analysis conducted in the lab confirmed one hybrid, whose mother was a capped langur and father a Phayre’s langur. Additionally, a female exhibiting hybrid traits was found to be a mother, suggesting that at least some hybrids are fertile and can reproduce.
Hybridization: A Fearful Yet Increasing Concern Globally
Although hybridization is uncommon among primates, it can occur where related species’ habitats intersect. Human activities like deforestation, habitat fragmentation, and primate hunting can lead to smaller, isolated populations, increasing the likelihood of hybridization. Tanvir Ahmed, the study’s lead author, expresses concern: ‘The presence of fertile hybrids is particularly worrisome, as it indicates that gene flow between these endangered species could permanently alter their genetic future.’ Christian Roos, the study’s lead scientist, stresses the broader implications: ‘This isn’t solely a local issue. As habitats are destroyed, animals mix improperly, resulting in hybridization that may lead to the extinction of one or both species.’
A Call to Action: The Importance of Forest Protection and Research for Conservation Efforts
The research also discovered that well-protected forests sustain higher populations of langurs than those that are poorly managed. Nevertheless, many of these forests are too small and disconnected to secure the species’ long-term survival. Tanvir Ahmed insists, ‘Prioritizing forest conservation nationally is crucial. Failure to act could lead to the loss of not only two monkey species but also a significant aspect of Bangladesh’s biodiversity.’ Alongside forest preservation, further research is essential to deepen our understanding of hybridization and to craft effective conservation strategies. Co-author Dietmar Zinner notes, ‘This study serves as a rallying point. We require more data to form effective, long-term conservation plans. Additional research will clarify the scope of hybridization, the effects of human interference, and strategies to mitigate the worst impacts.’
With fewer than 500 Phayre’s langurs and 600 capped langurs remaining in northeastern Bangladesh, action is urgently needed. Their survival hinges on immediate measures, including forest preservation and establishing corridors to connect their habitats.
Future Directions
As part of his doctoral research, backed by the German Primate Center and the German Academic Exchange Service (DAAD), Tanvir Ahmed will now undertake an extensive genetic study of langur populations and their susceptibility to climate change. The results are expected to contribute to a tailored action plan aimed at safeguarding langurs in Bangladesh.
