Rope bridges built for Hoolock gibbons in Lauachhara forest

Hoolock gibbons used to be found in large numbers in different forests of the country a few decades ago but they are now on the verge of extinction as the latest survey has found only 43 of the endangered species. 

Indiscriminate deforestation and hunting, and food and habitat crises are the main reasons for the decline in the numbers of gibbons.

Even though researchers say the habitat for gibbons is somewhat better in Sylhet's Lauachhara National Park in Moulvibazar, the rail tracks and roads that pass through the forest have divided the forest, causing problems for the animal.

To address the problem, the forest department, with the support of the zoology department of Jagannath University, has built five rope bridges across the inner railway lines and one across the road in Lauachhara forest.

Genetically, the animal is close to human beings. It swings from tree to tree and cameras have been installed at the bridges to test their success. Cameras will take photos of animals crossing the bridges. If successful, similar bridges will be built in other forests too.

A research team under the supervision of Dr Habibun Nahar, associate professor, Jagannath University, has taken this initiative funded by the Bangladesh Forest Department.

Professor Dr Sabir Bin Mozaffar from United Arab Emirates University, Md Sabit Hasan, Isabella Foundation Wildlife Researcher, Researcher Hasan Al-Razi, Nekam Field Manager Researcher Tanvir Ahmed, Jagannath University Zoology Department students Sajib Biswas and Tania Akter were also members of the research team.

Habibun Nahar said they built five bridges using ropes ( 10 centimetres in diameter), which will be a temporary solution to the problems caused by road and rail lines in the free movement of gibbons. 

Md Sabit Hasan said his latest survey found 43 members of 13 gibbon families in the Lauachhara forest.

Dr Habibun Nahar and Dr Sabir Bin Muzaffar have researched the number, family structure, and behaviour of gibbons in this forest for the last year, which was funded by the US Fish and Wildlife Service.

They said although the density of gibbons in Lauachhara forest is higher than in other forests, their living conditions are in dire straits. These artificial bridges will connect a few portions of the forest which will act as safe passage for the movement of other monkey species and arboreal animals. Furthermore, the number of monkey species that would die crossing roads and railways would also reduce.

Wildlife researcher Hassan Al Razi said a study was conducted on the deaths of monkeys in road accidents and electrocution in Lauachhara and Satchhari forests from 2015 to 2017. Although there is no evidence of gibbons dying in this study, roads and railways pose a major threat to them.

This initiative will help gibbons and other arboreal animals to cross the roads and railways safely. However, it will take a few months for gibbons to get acquainted with the bridges and get used to them, he added.

Apart from the forests of Sylhet, Chattogram and Chattogram Hill Tracts, gibbons are also found in India (northeast), Myanmar (west), and China (south). According to an International Union for Conservation of Nature survey, gibbons are in critical condition globally.

An adult gibbon is about 60 to 90 centimetres long and weighs six to nine kilograms. Although male and female gibbons are almost identical in size, there are significant differences in skin colour.

 The body of a male gibbon is black with white eyebrows and a female gibbon has grey-brown hair all over her body. Hair around the neck is blacker and eyes and mouth are covered with white fur, like a mask.

An adult gibbon gives birth to a baby after six to seven months of pregnancy. The lifespan of a gibbon is 25 years on average.