Cross-country conservation efforts needed for the Critically Endangered Raffles's Banded Langur
Raffles's Banded Langur Presbytis femoralis ©Lee Zan Hui
In July this year, the latest edition of ‘Primates in Peril: The World’s 25 Most Endangered Primates 2022-2023’ by the IUCN SSC Primate Specialist Group was revealed. Included in the list is the Raffles's Banded Langur Presbytis femoralis, which is listed as Critically Endangered in the IUCN Red List of Threatened Species in its December 2021 publication.The Raffles's Banded Langur occurs only in Singapore and southern Peninsular Malaysia. Its name is derived from Sir Stamford Raffles, a British colonial administrator and naturalist, who made observations about the langur in the early 19th century in Singapore.As Raffles’ Banded Langur and other Presbytis langurs have a general call structure of Srr-Ka-Ka-Ka-Ka-Ka, indigenous tribes in the region generally called the langurs as “Chĕnĕka”, “Chigak”, or “Kekah”, while they are known as “Lutong” in Malay.Initially, Presbytis femoralis consisted of three banded langur subspecies which ranged through Sumatra, Borneo, Peninsular Malaysia, southern Myanmar and southern Thailand. With non-invasive sampling and advanced sequencing technology providing genetic information, the three subspecies were listed as separate species 2021: Raffles’s Banded Langur, Robinson’s Banded Langur and East Sumatran Banded Langur.Raffles's Banded Langur’s change in taxonomic status and its small and vulnerable populations within a restricted range, led to its Critically Endangered status in the IUCN Red List. Its inclusion in the Top 25 Most Endangered Primates list reinforces the urgency of conservation attention and action needed to recover the species from the brink of extinction.
Raffles's Banded Langurs are born with white-grey fur. This pair was photographed in June 2018.©Sabrina Jabbar
Like many primate species around the world, the Raffles's Banded Langur is threatened by habitat loss and fragmentation. Records until the 1920s indicate that this langur was a common sight in forests in Singapore. However, rapid urbanisation in Singapore over the past 50 years as well as recent land developments in southern Peninsular Malaysia threaten the species’ continued survival. Earlier this month, two male langurs were found as roadkill along an express way in Singapore.In Singapore, the current population is estimated to be 70 individuals mainly confined to the nature reserves, while in southern Peninsular Malaysia, there is an estimated total population of several hundred individuals. However, deforestation due to land use change has resulted in a severely fragmented forest landscape, and population strongholds occur mainly within three forest fragments in Johor and Pahang.
Left: The global distribution range of the Raffles's Banded Langur. Right: A detailed map of the southern Malay peninsula and its forest canopy (in green), tree cover loss since 2000-21 (in dark red), tree cover gain since 2000-12 as likely growth of plantation in blue/purple). Green patches within the black outline are the remaining potential habitat patches of the Raffles's Banded Langurs. Map by Lee Zan Hui.
With an estimated fewer than 400 individuals of this species remaining globally, a Species Action Plan was developed collaboratively with 15 organisations in 2016. The plan highlights the need to restore habitat connectivity, conduct population research, as well as communicate findings and raise public awareness for the conservation of the species.Key goals of the Raffles’ Banded Langur Species Action Plan are to recover and protect its existing wild populations, gather key data through research and monitoring, and to secure the necessary resources for sustained survival of the species. One of the long-term plans for species recovery should address currently non-viable populations living in large but isolated forest fragments and supplement these with individuals from other populations, to build their population sizes to likely viability and restore gene flow between the Malaysia and Singapore populations. Previously, with each country having a much larger population, there was no risk of genetic propensity to extirpation, but today’s much-reduced populations require pro-active management and strategic collaborative long-term planning. Hence, the action plan aims to foster cross-country collaborative conservation action between governments, researchers, and conservation partners.As a result of the 2016 meeting, the Raffles Banded Langur Working Group was formed, bringing together relevant experts from government agencies, NGOs, and academic researchers from both range countries to help execute the species action plan.In Singapore, the Raffles Banded Langur Working Group, led by Andie Ang of Mandai Nature and Chair of the Working Group, has been carrying out population monitoring through the use of arboreal camera traps as well as a complementary citizen science programme. As part of the latter, volunteers are trained to regularly observe and collect population data. Andie and her team also identified key crossing areas and assisted the Singapore National Parks Board in establishing rope bridges at crucial crossing points between gaps in the forest canopy.
A Raffles's Banded Langur sitting on a rope bridge in Singapore, photographed in June 2020. Rope bridges, like the one pictured here, have been installed to facilitate movement of tree-dwelling wildlife in and around the Central Nature Reserves in Singapore. ©Sabrina Jabbar
In Malaysia, research groups from School of Biological Sciences, Universiti Sains Malaysia (USM) in collaboration with the Malaysian Primatological Society (MPS), as well as Universiti Tun Hussein Onn Malaysia, have conducted studies on Raffles's Banded Langur in some sites in Peninsular Malaysia in recent years. More studies to cover different habitat types and condition in Peninsular Malaysia is needed to gain better understanding on Raffles’ Banded Langur’s ecology and population status, where there is a more diverse and heterogenous landscape, as well as more sympatric primate species and wildlife with niches partition and potential competition.According to Nadine Ruppert and Lee Zan Hui of USM and MPS, most members of the public in Malaysia are unable to differentiate between the various langur species or are unaware that a highly threatened langur species occurs in their landscape, given the species’s relatively shy behaviour. In December 2021, MPS and WWF held a social media campaign to raise public awareness about the species, and they continue to engage with hikers who regularly visit recreational forest within the species range to lay the foundations for community engagement.In Singapore, the langurs are relatively well-known, due to the decade-long efforts by the people now constituting the Raffles’ Banded Langur Working Group. To date, they have given more than 50 public talks reaching close to 5000 people and they continue to recruit citizen scientists and encourage members of the public to keep reporting sightings of the langurs in the wild and to build a greater support network for the conservation of the species.“We consider this citizen science monitoring project a success, as it helped raise public awareness about the langurs, with over half of citizen scientists participating seeing this Critically Endangered primate that is otherwise rarely seen in the wild,”- Andie Ang, Chairperson of the Raffles' Banded Langur Working Group.While the Raffles's Banded Langur may be on the current ‘The World's 25 Most Endangered Primates’ list, it is heartening to see how concrete conservation action is underway in both range countries of the species. It is vital that continued collaboration and partnerships are maintained and strengthened in order to secure the species’ long-term survival.To find out more about the species, click here.Earlier this year, Andie Ang and Sabrina Jabbar of the Raffles' Banded Langur Working Group published a book on the Raffles's Banded Langur natural history and conservation efforts.ASAP Partners working to conserve Raffles's Banded Langur:
School of Biological Sciences, Universiti Sains Malaysia