Phibsoo Wildlife Sanctuary

Phibsoo Wildlife Sanctuary is a protected area in southern Bhutan, situated in western Sarpang district and southeastern Dagana district along the country's border with the Indian state of West Bengal. Covering 268.93 square kilometres, it is the smallest protected area in Bhutan. The sanctuary is distinguished as the country's only tropical lowland wildlife reserve, protecting a unique subtropical ecosystem that contrasts sharply with the mountainous terrain and temperate forests that characterise most of Bhutan. The area was first designated as Phibsoo Reserved Forest in 1974 and was upgraded to a wildlife sanctuary in 1993 as part of a nationwide revision of the protected areas system.^[1][2]

The sanctuary's primary ecological significance lies in its extensive sal (Shorea robusta) forests, which represent the last naturally occurring stands of this commercially valuable tree species in Bhutan. Phibsoo is also the country's only natural habitat for agarwood (Aquilaria) trees. These forests form part of the broader Terai-Duar ecosystem that stretches along the southern foothills of the Himalayas, a landscape that has been extensively cleared for agriculture and settlement in neighbouring India and Nepal. Phibsoo thus serves as a critical refuge for a habitat type that has become increasingly rare across the eastern Himalayan region.^[3]

The sanctuary plays a vital role in maintaining ecological connectivity within Bhutan's biological conservation complex. It is connected via biological corridors to Jigme Singye Wangchuck National Park to the north and, through the broader corridor network, to Royal Manas National Park to the east. Along the Indian border, it is linked to Petu Reserve Forest and Buxa Tiger Reserve in West Bengal. The Sunkosh River forms the sanctuary's western boundary and the Sanathang River its eastern boundary, both separating it from Indian territory. This transboundary connectivity allows for the movement of wide-ranging species such as Asian elephants, tigers, and gaur, contributing to the long-term viability of their populations in the region.^[1][3]

Geography

Phibsoo Wildlife Sanctuary occupies the subtropical lowlands and lower foothills of southern Bhutan, with elevations ranging from approximately 200 metres along the Indian border to around 1,600 metres at its northern extent. The terrain transitions from flat alluvial plains in the south to rolling hills and steeper slopes as it rises toward the Himalayan foothills. The sanctuary spans parts of Nichula and Singye gewogs under Dagana and Sarpang dzongkhags respectively. It is drained by several rivers and streams, including the Phibsoo and Longa rivers, which flow southward into India's Brahmaputra river system.^[1]

The climate is subtropical, with hot, humid summers and mild winters. The monsoon season brings heavy rainfall from June to September, sustaining the dense tropical and subtropical forests that blanket the sanctuary. The forest types are classified as subtropical semi-evergreen forest, subtropical moist deciduous forest, and subtropical moist evergreen forest. This combination of warmth and moisture creates ideal conditions for the sal-dominated forests that define the sanctuary's character.^[3]

Biodiversity

Phibsoo harbours approximately 637 species of flowering plants, over 40 species of mammals, and at least 132 recorded bird species. The dominant vegetation type is sal forest, with Shorea robusta forming dense canopies interspersed with other tropical species including Terminalia, Lagerstroemia, and various bamboo species. Grasslands and riverine habitats along the sanctuary's waterways add to the diversity of plant communities.^[3]

The sanctuary is home to a remarkable assemblage of mammals, notably all eight cat species found in Bhutan. The Asian elephant (Elephas maximus) is the sanctuary's flagship species, with herds moving between the sanctuary and adjacent protected areas in India. The gaur (Bos gaurus), the world's largest wild bovine, inhabits the sanctuary's forests and grasslands. The Royal Bengal tiger (Panthera tigris tigris) has been confirmed through camera trap surveys. Phibsoo is the only place in Bhutan where chital or spotted deer (Axis axis) occur naturally. Other notable mammals include the clouded leopard (Neofelis nebulosa), Asiatic golden cat (Catopuma temminckii), dhole or Asiatic wild dog (Cuon alpinus), rhesus macaque (Macaca mulatta), large Indian civet (Viverra zibetha), Indian grey mongoose, and Indian crested porcupine. The sanctuary also represents the westernmost limit of the endangered golden langur (Trachypithecus geei), a primate endemic to the region between the Manas and Sankosh rivers.^[3][4]

The avifauna is exceptionally rich for Bhutan's lowland areas. The sanctuary hosts four species of hornbill, including the great hornbill (Buceros bicornis), rufous-necked hornbill (Aceros nipalensis), and wreathed hornbill (Rhyticeros undulatus). Other notable bird species include the Indian peafowl, grey peacock pheasant, spot-winged starling, black stork, Blyth's kingfisher, collared falconet, black-backed forktail, white-winged wood duck, Himalayan griffon vulture, and rose-ringed parakeet. The sanctuary's rivers, particularly the Phibsoo and Longa, provide habitat for the critically endangered white-bellied heron (Ardea insignis), one of the world's rarest birds with fewer than 250 individuals remaining globally; two individuals were recorded in the sanctuary in 2014. Three species of mahseer fish inhabit the sanctuary's rivers, and the presence of the Ganges river dolphin has been considered possible.^[3][5][1]

Cultural Significance

The communities living in and around Phibsoo Wildlife Sanctuary are predominantly Lhotshampa (ethnic Nepali Bhutanese), who have historically practised subsistence agriculture, livestock rearing, and forest resource harvesting in the region. The forests of southern Bhutan have long held spiritual significance for local communities, with sacred groves and forest deities forming part of the cultural landscape. The Bhutanese refugee crisis of the late 1980s and 1990s significantly affected the demographic composition of the sanctuary's buffer zone, as many Lhotshampa residents were displaced. The sanctuary itself has no permanent human residents within its boundaries.^[1]

Conservation

Originally designated as Phibsoo Reserved Forest in 1974, the area was upgraded to a wildlife sanctuary in 1993. Despite this formal status, the sanctuary long remained what conservationists term a "paper park", with minimal management presence. Conflicts in the region during the 1990s further delayed conservation efforts. Active management only commenced around 2009, and the sanctuary gained operational independence from the Sarpang Forest Division in 2014, following the approval of its first conservation management plan in 2012. It is managed by the Department of Forests and Park Services and forms part of Bhutan's broader network of protected areas and biological corridors.^[2][1]

Human-elephant conflict is the most pressing conservation challenge facing the sanctuary. As elephants move between the sanctuary and surrounding agricultural areas, they frequently damage crops and property, creating tensions with local farming communities. The government has implemented various mitigation measures, including electric fencing, early warning systems, and compensation schemes for affected farmers. Transboundary cooperation with India is essential, given the sanctuary's connections to Buxa Tiger Reserve and other Indian protected areas. Habitat degradation from illegal logging, encroachment, and the spread of invasive plant species also pose ongoing threats to the sanctuary's ecological health.^[1][3]

Tourism

Phibsoo Wildlife Sanctuary receives very few visitors compared to Bhutan's more accessible protected areas in the western and central regions. The sanctuary's remote southern location, limited infrastructure, and challenging terrain have restricted tourist access. However, the sanctuary offers significant potential for nature-based tourism, particularly birdwatching, wildlife viewing, and trekking through pristine tropical forests. Its four hornbill species and the chance of observing the critically endangered white-bellied heron make it a destination of particular interest to birdwatchers. Visitors typically access the sanctuary through Sarpang or Gelephu, the nearest towns with road connections.^[3]

References

1. "Phibsoo Wildlife Sanctuary." Wikipedia.
2. "Phibsoo Wildlife Sanctuary." Bhutan Biodiversity Portal.
3. "Phibsoo Wildlife Sanctuary." Wild Nature Quest / Bhutan Birding.
4. "Population abundance and distribution of the endangered golden langur in Bhutan." Primates, Springer, 2019.
5. "Strengthening conservation of critically endangered White-bellied Heron." Royal Society for Protection of Nature, Bhutan.