Canopy bridge project saving at-risk monkey species from extinction

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The Sigiriya-Inamaluwa main road in the hill country is a busy road. This road is of utmost importance because it is situated at the main entrance to the famous Sigiriya rock, also known as the Lion Rock. Tourists and locals frequently use this road to access the historical rock fortress built in the 5th Century.

But unknown to many and deep in the jungles of the surrounding area live many animals, that also include the Purple-faced leaf monkey (Semnopithecus vetulus). But today this busy road has sounded the death knell for the species.

These monkeys use trees to move from one forest to another. We see them swinging from one branch to another and crossing over from one forest to another. With their babies on their backs and some single, these monkeys can be seen in groups journeying from one thick forest to another in search of food.

When they have no trees and branches, the monkeys use the roads to get from one jungle to another. Deforestation and continuous loss of habitat has left the Purple-faced leaf monkey with no option but to cross roads when going in search of food. 

The Sigiriya-Inamaluwa main road is one such road that is often used by the Purple-faced leaf monkey to get to the other side of a jungle. But some don’t make it to the other side as they are knocked down by vehicles. Some monkeys die and others are left with life threatening injuries and roadkill are frequently reported in this area. The Purple-faced leaf monkey population is on the decline due to frequent roadkill.        

Canopy bridge

The Purple-faced leaf monkey is classified as Endangered by the International Union for Conservation of Nature (IUCN, 2015), appearing on the IUCN’s Red List of Threatened Species. Then came an idea from the Wildlife and Nature Protection Society (WNPS). An idea that would save the Purple-faced leaf monkey from road kills – a canopy bridge.  

It all started when Hemas Consumer Brands told the WNPS they can fund 25 small projects on endemic species, plants and animals among others. The WNPS then came up with the proposal to build a canopy bridge for the Purple faced langhur on the Sigiriya-Inamaluwa main road after they learnt that there are many roadkills.

“There are other canopy bridges in the country. But since the Sigiriya-Inamaluwa main road has caused the deaths of Purple-faced leaf monkeys the WNPS decided to build a canopy bridge in the area. The langurs when crossing from one part of the jungle to the other side get knocked down by vehicles. By building this bridge we hope to reduce the number of road kills in this area in the future,” President WNPS Jehan Canagaretna told Ceylon Today.”

He says we have used two strong wires on either side of the bridge and fencing net in the middle. “We have to monitor the situation from now on. When one monkey starts using the bridge the others will follow because they know it is safe to use. We have completed 12 projects up to now and will complete the remaining projects by the end of this year,” Canagaretna said.

Sigiriya-Inamaluwa main road

The main person behind the project is WNPS District Representative, Matale Thusitha Weerasinghe. “The main entrance to the famous Sigiriya Rock is on the Sigiriya-Inamaluwa main road. When tourists come to Sigiriya to climb the rock there is a lot of vehicle movement. The forest area has many Purple-faced Leaf Monkeys. These monkeys use the main road to cross from one side of the forest to the other. When trying to cross the road some get knocked down,” says WNPS District Representative, Matale Thusitha Weerasinghe.

He goes on to say that no research has been done on the numbers that die but he thinks around 20 to 25 Purple-faced leaf monkeys perish per year. 

“There are two archaeological sites at Sigiriya. The Rama Kele Archeological site and the Sigiriya sanctuary. The Purple faced leaf monkey crosses from one archaeological site to the other. After recommendations by the Department of Wildlife Conservation (DWC) the most suitable location to set up the canopy bridge was chosen. To reduce the number of road kills the canopy bridge was put up on the Sigiriya-Inamaluwa main road,” Weerasinghe explained.

He says the canopy bridge that is 60 feet long was put up close to the DWC Range office in Sigiriya. “The bridge was put up in one day on 13 March 2022. Around eight people that included DWC officers and WNPS officials worked on the project,” Weerasinghe said.   

Endemic to Sri Lanka

The Purple faced leaf monkey endemic to Sri Lanka uses trees to go from one place to another he says but the monkeys didn’t use the bridge soon after it was built. “After a few days they got used to the presence of the bridge and were recently seen using it to cross over to the other side. The macaques were also spotted using the bridge. We hope the Grey Slender loris, the Grey langur, the Golden palm civet endemic to Sri Lanka who can be seen in this area, will also use this bridge,” Weerasinghe explained.

He says there is no big maintenance for this type of bridge. “We want to make this bridge more natural by sending a creeper through the trees and to the bridge, so that in about two to three years the bridge will get covered by the creeper and become a natural part of the environment,” Weerasinghe said.

Plans are now underway by the WNPS to erect a second bridge in Attidiya. “We hope to erect the second canopy bridge in the Attidiya marsh area in September 2022 or October 2022. There are no road kills in the Attidiya area but the monkeys cannot cross from one side of the island to the other side because of the canals. We hope this canopy bridge will help the monkeys to move from area of the island to the other,” Canagaretna explained.      

He says the canopy bridge set up at Sigiriya is proving to be extremely useful and the WNPS would continue this in a few urban areas as well. “The next one will be at the WNPS Green Isle wetland at Attidiya. The Sigiriya-Inamaluwa main road bridge costs Rs 62,000 to build. But we don’t know how much the second bridge will cost since all products have gone up in price now,” Canagaretna said. 

Sri Lanka black monkey

In Sinhala the Purple-faced langur is known as the Sri Lanka black monkey. The males are usually larger than females.  According to the Mammals of Sri Lanka, the four subspecies are recognized as the Southern lowland wet zone purple-faced langur, Semnopithecus vetulus vetulus, the Western purple-faced langur or North lowland wet zone purple-faced langur, Semnopithecus vetulus nestor, the Dry zone purple-faced langur, Semnopithecus vetulus philbricki which is the largest subspecies and the Montane purple-faced langur or Bear Monkey, Semnopithecus vetulus monticola.

The Purple-faced langur is found in closed canopy forests in Sri Lanka’s mountains and the southwestern part of the country, known as the “wet zone”. Deforestation has resulted in the langurs home ranges to be exposed to direct sunlight and the Purple-faced langurs are most often found in small and widely scattered groups. Ninety percent of the langurs range, now consists of human populated areas.

Its range has constricted greatly in the face of human encroachment, although it can still be seen in Sinharaja, Kitulgala, Kandalama, Mihintale, in the mountains at Horton Plains National Park or in the rainforest near the city of Galle.

(Pix by Ashan Wijetilleke)

By Risidra Mendis