Saving Primates of Bangladesh From Extinction

Estimated reading time: 9 minutes

Study finds that interbreeding between critically endangered primates of Bangladesh Phayre’s langurs and endangered capped langurs raises serious concerns about their future survival as distinct species. Species hybridisation is a sign of ecological disruption, and researchers point to human-related threats such as palmoil and timber deforestation, habitat fragmentation, and hunting as key drivers for them interbreeding. These pressures not only push the species to hybridise but also threaten their long-term existence in the wild, highlighting the urgent need for conservation efforts to address habitat destruction and protect these seriously endangered primates.

This article was originally published in Mongabay and was written by Mohammad Al-Masum Molla, read the original article. Republished under Creative Commons attribution licence. Research by Ahmed, T., Hasan, S., Nath, S., Biswas, S. … Roos, C. (2024). Mixed-Species Groups and Genetically Confirmed Hybridization Between Sympatric Phayre’s Langur (Trachypithecus phayrei) and Capped Langur (T. pileatus) in Northeast Bangladesh. International Journal of Primatology. doi:10.1007/s10764-024-00459-x

---

Hybridisation: a major concern for Phayre’s and capped langurs

This hybridisation of the endangered primates, which researchers of the study say is caused by habitat loss due to deforestation and other human interferences, could push them to extinction in a few generations.

“Bangladesh’s langur populations are small and isolated, limiting gene flow. This hybridisation in restricted populations heightens their extinction risk. Furthermore, our laws primarily protect pure langurs, leaving hybrids unprotected. If hybrids persist into future generations, we’ll face tough decisions about their role in our ecosystem,” Tanvir Ahmed, the study’s lead researcher, told Mongabay.

Interbred langurs grow up to be infertile

Monirul H. Khan, a professor at Jahangirnagar University’s Zoology Department, agreed with Tanvir and said that the significance of interbreeding is that these langurs don’t survive for a long time.

“They are usually born infertile. So the population of langur will gradually decrease,” he said.

The study, published in the International Journal of Primatology, recently found that out of 98 langur groups observed, eight comprised both Phayre’s and capped langurs.

“We analysed genetic samples of the species in the lab and confirmed one case of hybridisation. This langur had a capped langur mother and a Phayre’s langur father. Another female with a hybrid appearance showed signs of motherhood, indicating that at least female hybrids are fertile and give birth to young,” Tanvir said.

“The genetic characteristics of a distinct species tend to become most threatened when their hybrid females can reproduce. Fertile hybrid females threaten to bring the two species closer together as the offsprings begin to mix characteristics. That is exactly what could be happening to them,” he said.

Both species stand to lose as genetic traits don’t get passed on

The research shows that the ‘spectacled’ Phayre’s langurs and the capped langurs, with their distinctive shock of black fur on their heads, are under threat of losing their distinct genetic makeup to hybridisation.

Researchers conducted the study over five years, between 2018 and 2023, in six forests in northeastern Bangladesh — Lawachara National Park, Satchari National Park, Rema-Kalenga Wildlife Sanctuary, Rajkandi Reserve Forest, Patharia Hill Reserve Forest and Atora Hill Reserve Forest.

The study involved field surveys for 92 days between March 2018 and April 2019 and from July to December 2022, employing three trained local eco-guides to monitor the mixed-species groups until October 2023.

Habitat loss puts many species under pressure

The study shows that, although it’s relatively rare, hybridisation among primates is an escalating concern worldwide, often driven by habitat loss and fragmentation. It serves as a stark reminder of the significant impacts of human activity on biodiversity. The situation in Bangladesh gradually becoming more common emphasizes the urgent need for strong conservation efforts.

The study mentions how hybridisation is a vital indicator of ecological change, raising serious concerns about species’ genetic health. Tanvir added that this study is groundbreaking, as it documents the first hybridisation incidents among these langurs in Bangladesh and their entire distribution range.

Hybrids being fertile could lead to the extinction of the parent species. “Additionally, mixing species can enable the spread of diseases between previously unconnected populations, posing risks to both wildlife and human health, since these animals are often hunted and traded,” said Sabit Hasan, a researcher of the study.

Deforestation, habitat fragmentation and hunting

The study blamed human activities such as palm oil deforestation, habitat fragmentation, hunting and trapping of primates as some of the causes that can increase the risk of such hybridisation.

“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 composition,” Tanvir said.

The beautiful primates of Bangladesh

Ten of the 121 mammal species found in Bangladesh are primates. According to the hybridisation study, Bangladesh is home to less than 500 Phayre’s langurs and 600 capped langurs.

The Phayre’s langur has a brown to grey-brown back, white fur on its belly and face, and a “spectacled” appearance due to wide white rings around its eyes. Its face and extremities are black, and it has long hair on its head that points backward. Additionally, its tail is longer than its body and has a tuft of dark hair at the tip.

The capped langur is known for its distinctive crown of long, erect hairs on its head. It has a black face, grey to blackish-grey fur on top, and brownish-yellow or orange fur below, with the distal half of its tail being blackish.

The study suggested the government prioritize habitat preservation and create corridors to connect isolated primate populations, facilitating natural langur dispersal.

“If we don’t take action now, we risk losing not just two monkey species but also a vital part of Bangladesh’s biodiversity,” Tanvir said.

Banner image: The genetically confirmed hybrid (right) with its capped langur mother at Satchari National Park. Image by Harish Debbarma.

This article was originally published in Mongabay and was written by Mohammad Al-Masum Molla, read the original article. Republished under Creative Commons attribution licence. Research by Ahmed, T., Hasan, S., Nath, S., Biswas, S. … Roos, C. (2024). Mixed-Species Groups and Genetically Confirmed Hybridization Between Sympatric Phayre’s Langur (Trachypithecus phayrei) and Capped Langur (T. pileatus) in Northeast Bangladesh. International Journal of Primatology. doi:10.1007/s10764-024-00459-x

ENDS

---