Phayre’s langur can act as an umbrella species for northeastern Bangladesh. Photo: Tanvir Ahmed

Highlights

• Phayre's langur, a species of primate, appears to be three different species now

• Rivers and mountains act as key factors in speciation of this South Asian monkey 

• Its entire range has been cut and distributed among three species

• The taxonomy makes each one even more threatened 

• The newly split Popa langur is already under grave threats, restricted to a single mountain of Myanmar with only 250 individuals left in the wild

• There are 400 individuals of Phayre's langur still living in the forests of Sylhet. The fact came to us this year

• Forests of eastern Bangladesh, if treated with care, can be an ideal refuge for the ever-diminishing Phayre's langur

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The monkey is spectacle-faced. Lithe build, long muscular tail and brachiating appendages make it a master tree-dweller. Slate grey shaggy coat with white underside and blue-rimmed white patches around eyes readily separate it from any other primate kins. 

Its love for leaf and foliage puts it in a particular group called leaf monkeys. This goggle-eyed leaf monkey is often called Phayre's langur, commemorating the name of British Indian Army officer and naturalist Sir Arthur Purves Phayre. 

Until recently, Phayre's langur was thought to have spread from eastern Bangladesh and northeast India to the deep forested regions of central Myanmar and southwestern China. A 2020 study published in the journal Zoological Research established the long-suspected claim: The region has more than one species of Phayre's langur. 

In fact, now, we know that there are three different species. 

Tanvir on his first encounter

Tanvir is a zoology graduate from Jagannath University. It has been a couple of years that he is focusing on Phayre's langur. I approached him about the astounding discovery, only to find him as a part of the researchers who carried out the investigation! 

Baffled, I asked him how he started his journey. 

"Six years ago, I made my first visit to Satchari National Park (SNP), a designated protected area in Habiganj. I was there to watch wildlife. The wintry morning tuned with cicada's jhee jhee calls and birds' medley chirping was very welcoming. 

"I felt peace in the wilderness and luck favoured enough for that day! While coming out of the forest, I spotted a spectacle-faced monkey. It was a mother with a small baby clinging to its belly! I had never seen such a cute face in my life! The next day was spent in Lawachara forests in Moulvibazar and the spectacle faces overwhelmed me again. I decided to understand them," he gave me a love-at-first-sight story. 

Phayre’s langur is a critically endangered species in Bangladesh. Photo: Abu Bakar Siddik

Disappearing canopy-blazers

I could recall the welcoming troops of Phayre's langurs at the entrance to SNP back in 2009. The case is different now. With forest destructions, fragmentations, loss of canopy intactness, illegal hunting for bush-meats and trading of private zoos, the species is becoming a rarity everywhere. 

Its existence is at threat in all the seven range countries. The International Union for Conservation of Nature and Natural Resources (IUCN) categorised the species as critically endangered in Bangladesh. 

This means the species has lost over 80 percent of its population in the last 30 years. It is said that the monkey lives in the forests of Sylhet and Chattogram divisions with a patchy distribution, with no more than 50 individuals in each population.

Male of the newly described Popa langur. Photo: Thaung Win

Bangladesh: Still a stronghold

Tanvir, at this point, pointed out a colossal paucity. He noticed a dearth of the species-specific information in Bangladesh when compared to the global distribution. Elusive tendency and disappearing trend were making the species the least priority, which, in turn, was feeding its ultimate demise from Bangladesh. 

Learning all these, he felt incredibly sad and searched every way to help it out. He teamed up with Sabit Hasan, Shimul Nath and Sajib Biswas, and surveyed the forests of Sylhet division. With support from the Bangladesh Forest Department, Jagannath University and scientists from many countries, they hit a breakthrough. 

The work shed new light on the available information of the species. An estimated total of 400 individuals appeared to be still surviving in northeast Bangladesh. 

Mount Popa, the habitat of the newly described langur. Photo: Thaung Win

When taking the forests of Chattogram and Chattogram Hill Tracts into account, a staggering fact can be projected. The country is still a stronghold for Phayre's langur, and there is still time to avert their extinction. 

There is more to know!

While engaging monkey scientists in the last couple of years, Tanvir was hit with an amazing fact: There are morphological and genetic variations in Phayre's langur across the global distribution. 

Colleagues from Germany and Myanmar picked up the question and headed a research to revise the taxonomy of Phayre's langur collaborating with multinational researchers from nine different countries. Tanvir joined the team. 

The study included physical examinations of collected Phayre's langur specimens preserved in the natural history museums across three continents. For molecular genetics study, faecal samples of wild langurs were collected. Fur and tissue samples were also extracted from the museum specimens. Finally, genetic studies were conducted at the German Primate Centre.

It was surprising to the scientists when specimens collected over a hundred year ago represented a different lineage in genetic study. South African mammalogist Guy C Shortridge collected a specimen from the sacred Mount Popa of Myanmar in 1913. It was later preserved in the Natural History Museum in the UK.  

The newly described leaf monkey was named Popa langur following the first place of collection. Genetically, Popa langur diverged from the sister species about a million years ago. 

Bounded by rivers and mountains

Now, the leaf monkeys of Bangladesh, India and Myanmar belong to three different species. All are separated by some mighty rivers. The largest distribution is still held by Phayre's langur Trachypithecus phayrei. 

This species reigns the whole region to the west of the Chindwin River and the Ayeyarwady River. The remaining two species are chipped between the Ayeyarwaddy River and the Thanlwin River. The Kayah-Karen Mountains separated Popa langur Trachypithecus popa from Shan State langur Trachypithecus melamera. However, the scientists believe that some intermixing might occur between the latter two.

Shan State langur in the Yadanabon Zoo. Photo: Chlidonias

Explained taxonomy, mounting threats

To get into the newly unravelled systematics of the Phayre's langur, I looked upon the map. On the contrary, I immediately sensed an intimidating fact. Tanvir agreed with the graveness of the situation. 

The restricted distribution of Popa langur, a Myanmar endemic, supports a maximum of 250 individuals. Researchers marked the newly described species as critically endangered. 

Phayre's langur remains with only one-third of its previously described range. Although it is threatened, scientists suspect the condition is far worse for Phayre's and Shan State langur. 

For Phayre's, Tanvir stressed Bangladesh as the last hope. I looked at the map again. The northeastern forests and patches of Chattogram coastal hills seemed hopeful. These forest patches draw the western margin of the Indo-Burma hotspot and are unbelievably rich in biodiversity. 

Despite the odds, they are easier to manage and are already in some form of protection when compared to the restive forests of Myanmar. I try imagining a safe refuge for Phayre's langur in these forests. In turn, the monkey starts appearing like a guardian as if it were in the Ramayana. The thought resonates optimism for conservation. 

Having a guardian species for each of our forests will be a milestone to celebrate. I adjust my crosshair with hope and positivity.