Lawachara National Park, a protected forest spanning 1,250 hectares in Moulvibazar district, is home to rich biodiversity and is one of the last remaining strongholds of the critically endangered hoolock gibbons in the country.

In 1996, the government officially declared Lawachara forest a national park under the Wildlife Act of 1974, recognising its immense ecological value.

The forest currently hosts 460 species of flora and fauna, including 167 species of plants, four amphibians, six reptiles, 246 birds, and 20 mammals.

The park has garnered international attention for the critically endangered primates thriving there, particularly the hoolock gibbons.

Once widespread in the country's natural forests, the hoolock gibbon population plummeted by around 80 percent, from over 3,000 to approximately 400, due to deforestation and habitat loss over the past 30 years, according to Forest Department sources.

A recent study by researchers from Jagannath University found that 13 hoolock gibbon families, comprising approximately 48 primates, are currently thriving in the forest. More hoolock gibbon families have been identified in the adjacent Kalachara and Chautali forests.

"My latest survey found 48 primates from 13 gibbon families in the Lawachara forest. Still, there is room for more gibbons to thrive in Lawachara. Proper habitat management initiatives are urgent for gibbons in this semi-evergreen habitat," said Sabit Hasan, a researcher.

Although the population density of gibbons in Lawachara is higher than in other forests, their habitat is still facing anthropogenic pressure from habitat destruction, he added.

"Hoolock gibbons closely resemble monkeys but are distinguished by their tailless bodies, long limbs, and striking colour differences between males and females. Their white eyebrows further set them apart," said Shyamal Debbarma, who has been involved in multiple studies on the primate species.

An adult hoolock gibbon typically measures between 60-90 centimetres in length and weighs between 6-9 kilogrammes. While males and females are similar in size, their body colours differ significantly. Males have black skin with white eyebrows, whereas females have grey-brown fur, with darker patches near the throat and neck. Females also have distinctive white fur around their eyes and mouth, resembling a mask.

Hoolocks give birth after 6-7 months of gestation. The babies are initially covered in fuzzy white fur, which darkens to black or brownish-grey within six months, depending on the sex. They reach adulthood at around 8-9 years of age and can live up to 25 years.

"The gibbons' existence is severely threatened due to rampant deforestation, habitat destruction, and food shortages. These primates are territorial and do not mix with other groups. They survive on fruits such as figs, chapalish (wild breadfruits), cowpea, berries, and banyan, as well as bamboo leaves and young tree shoots," said Md Shahidul Islam, former range officer of the Wildlife Management and Nature Conservation Department.

To ensure the gibbons' survival, conservation efforts have ramped up in Lawachara. Authorities are planting fruit-bearing trees such as figs and chapalish to ensure a stable food source for the gibbons. These efforts have seen the primate population gradually rise in Lawachara, unlike other areas where their populations are dwindling.

However, experts warn that habitat loss and food shortages continue to threaten the survival of the species and call for urgent action to protect these primates before they disappear from the country's forests entirely. This includes sustained habitat protection, reforestation efforts, and stringent policies to curb deforestation.

According to the International Union for Conservation of Nature (IUCN), these gibbons are classified as critically endangered both nationally and globally.