The number of one-horned rhinoceros in Bardiya National Park (BNP) is declining despite years of success in controlling poaching, with conservation officials blaming dwindling water sources, shrinking grasslands and a shortage of wallowing ponds, all compounded by growing human pressure.

The BNP, the largest national park in lowland Tarai covering an area of 968 square kilometres, counted 38 rhinos in its 2021 census. According to the park administration, seven rhinos died over the past five years mainly due to fighting.

Around 20 rhinos were believed to have crossed into India’s Katarniaghat Wildlife Sanctuary through the Khata corridor over the past two years, mainly due to water shortages.

Authorities have not conducted fresh surveys to track the endangered species. The census scheduled for 2025 was postponed because of a funding shortage, leaving the exact current population uncertain. Conservationists are worried regarding the declining rhino population in Bardiya.

“Even though the number of rhinos has declined, they are not on the verge of extinction,” said Mahesh Neupane, information officer at the park. “Rhinos naturally cross the border, and since they don’t stay in one place, those that reach India can return to Bardiya.”

Conservationists, however, are less confident about their return. Bijaya Raj Subedi, chief of the Division Forest Office in Bardiya, said Katarniaghat has sufficient water and grasslands, making it a more attractive habitat for rhinos that have crossed from Nepal.

Conservationists say Indian authorities have in recent years developed grasslands, water, and wallowing facilities in the sanctuary for rhino conservation.

The Geruwa river, a major offshoot of the Karnali, is at the centre of the problem. Its flow has declined as the river has gradually changed course, while floods and sediment deposits have altered the riverbed. The Geruwa coastal area is the main habitat of rhinos and other large mammals in western Bardiya.

“Safe habitat, adequate food and water throughout the year need to be managed,” said Ramesh Kumar Thapa, a former chief conservation officer of the park. “The narrowing of biological corridors, expansion of settlements, roads and other human activities have also become problems.”

Several streams in and around Bardiya dry up during the winter months. The Karnali river is the park’s main natural water source, but part of its flow is diverted for irrigation, while the Geruwa receives less water after changes in the river’s course. The park has built around 200 artificial ponds, but conservationists say these are not enough for large animals such as rhinos, which need natural water bodies and grasslands.

Ajit Tumbahamphe, Bardiya programme chief of the National Trust for Nature Conservation, said the shortage of natural water had pushed wildlife towards India through the Khata bio-corridor. The 24-km corridor links Bardiya with Katarniaghat, allowing rhinos, tigers, elephants and other animals to move across the border.

The decline is also reflected in deaths. Seven rhinos—four males and three females—have died in Bardiya over the past five years, according to Neupane. Several died in territorial fights as they competed for increasingly limited habitat.

On August 1, a male rhino of about 20 to 22 years was found dead after apparently fighting another rhino at Saijanghat along the Geruwa river. In April a rhino calf was found dead after a tiger attack in Shiva Community Forest. Three other rhinos died after fights in 2024 and 2022, while one was killed by a tiger and another died of natural causes.

Neupane said better habitat management could help reduce conflicts among rhinos, particularly by expanding grasslands and water sources. The park said a donor organisation plans to fund new ponds, grasslands management and habitat improvements this year.

Bardiya’s rhino population has also been shaped by past translocations. Between 1986 and 2000, 83 rhinos were moved from Chitwan to the Babai Valley and Karnali river area. Park records show 36 were killed by poachers during Nepal’s armed conflict between 1996 and 2006 and 24 died from natural causes. No rhino poaching has been reported in Bardiya for nearly two decades.

Thapa says habitat management now needs to be treated as urgently as security. He proposed keeping rhinos in a scientifically managed, secure enclosure of at least 500 hectares for breeding and gradually releasing them into natural habitat after their numbers increase. “This model is used in national parks in India and South Africa, but it has not been introduced in Nepal. It could be suitable here,” he said.

Neupane believes that without reliable water, adequate grasslands, wallowing sites and safe corridors, Bardiya’s rhinos will remain under pressure.

The one-horned rhino, which is native to Nepal and India, is an endangered animal species. According to the national rhino census held in 2021, Nepal is home to 752 one-horned rhinos. The rhinos are found in four protected areas in the country—Chitwan National Park, Bardiya National Park, Shuklaphanta National Park and Parsa National Park. According to the census, Chitwan National Park alone hosts 694 rhinos while Bardiya National Park has 38, Shuklaphanta National Park has 17 and Parsa National Park has three.