Forest loss forces langur species to interbreed, study finds

Research shows a threatening development for two endangered primate species in Bangladesh: the Phayre’s langur (Trachypithecus phayrei) and the capped langur (Trachypithecus pileatus). In mixed groups of these two species, hybrids have been found and genetically confirmed. If hybridization continues, it could mean the extinction of one or both species.

The article is published in the International Journal of Primatology.

For five years (2018-2023), an international team of researchers led by Tanvir Ahmed, a Ph.D. student at the German Primate Center, studied langur populations in northeastern Bangladesh. They found that 8 of the 98 langur groups studied consisted of Phayre’s langurs and capped langurs, and that in three groups, some individuals appeared to be a mixture of the two species.

Later, researchers analyzed genetic samples of the species in the laboratory of the German Primate Center and confirmed a case of hybridization. This langur had a mother capped langur and a father Phayre langur. Another hybrid-looking female showed signs of maternity, indicating that at least hybrid females are fertile and give birth to young.

Hybridization is generally rare among primates but occurs in areas where the ranges of related species overlap. Human activities such as deforestation, habitat fragmentation, hunting and trapping of primates, leading to population thinning and limiting the movement of individuals between local populations, may increase the risk of such hybridization.

Ahmed, lead author of the study, said: “The existence of fertile hybrids is particularly alarming because it suggests that gene flow between these two endangered species could irreversibly affect their future genetic makeup. »

Christian Roos, lead author of the study, highlights the global relevance of the research findings: “This is not just a local problem. When habitats are destroyed, animals mix abnormally and form mixed groups and hybridization can occur. It can even mean extinction. of one or both species.”

Urgent action is needed: forest protection and research as keys to conservation strategies

The study also showed that well-protected forests have a higher langur population density than less protected forests. However, these forests are often too small, too isolated and fragmented to ensure the long-term survival of the species.

“Forest conservation must become a national priority. If we do not act now, we risk losing not only two species of monkeys, but also a significant part of Bangladesh’s biodiversity,” says Ahmed.

In addition to protecting forests, continued research is needed to better understand the effects of hybridization and develop appropriate conservation strategies.

Dietmar Zinner, co-author of the study, summarizes: “This study is a wake-up call. We need more data to develop effective long-term conservation strategies. activities and how to prevent its worst effects.

With fewer than 500 Phayre’s langurs and 600 caped langurs in northeastern Bangladesh, time is running out for these species. Their survival depends on immediate actions, including both the conservation of forests and the creation of corridors for the dispersal of species between forests.

As part of his doctoral project supported by the German Primate Center and the German Academic Exchange Service (DAAD), researcher Ahmed is now focusing on a large-scale genetic study of langur populations and their vulnerability to change climatic. The results are expected to contribute to a tailored action plan for the protection of langurs in Bangladesh.