• Declining fish stocks in Nepal’s Koshi River threaten the predatory crocodile, which is already under pressure from historic poaching and habitat loss.
  • Crocodiles are increasingly encroaching on community-run fish farms in the buffer zone of the Koshi Tappu Wildlife Sanctuary in search of food, increasing the risk of conflict with humans, a new study shows.
  • At the same time, they face competition from gharials, mainly pescatarian crocodiles, which have been reintroduced to Koshi as part of a government-run conservation programme.
  • “It makes no sense for a sensitive species to compete with its endangered cousin,” says one of the study’s authors.

KATHMANDU – During extreme weather events, they can burrow, run on land and eat almost anything. These features, among others, make predatory crocodiles (Crocodylus palustris) a versatile species that can adapt to change.

“As part of the study, we counted the number of poachers in the reserve and its buffer zone where households and communities operate special fishponds supported by the wildlife reserve,” said Divya Bhattrai, lead author of the study and a researcher at Nepal’s University of Agriculture and Forestry. “We also assessed the threats thieves face in their homes.”

The Koshi Tappu survey was conducted during Nepal’s winter, from mid-September to mid-December 2020, when thieves come out to bask in the sun and are easier to spot. Bhattarai and his team observed 35 thieves, up from 16 recorded in 2013. “This number may increase as we survey not only the protected area but also the private and public ponds of the adjacent buffer zone,” he said. Of the 35 individuals recorded, 19 were observed in the buffer zone next to community and private fishponds.

Researchers say that while easy harvesting in fish farms may attract crocodiles to villages, other factors also keep them away from the river. According to the study, the wildlife sanctuary issued 466 licenses to local communities to fish in a small stretch of the river. However, many license holders were found to be fishing more than their allotted quota and many unlicensed fishermen are also operating in the area. “Fishermen have told us that their productivity has also gone down in the last few years,” Bhattarai said.

The researchers also found that bandits rarely appear to be in danger when moving among people living close to their homes. Human disturbance, distance to settlements and even roads have little effect on their spread. “We found that one of the communities was worshiping robbers as their main deity,” Bhattarai said.

This means that the robbers were given the right to enter the fish ponds at any time. Ashish Bashyal, a conservationist who was not involved in the survey and a member of the IUCN’s Crocodile Specialist Group, says that for most villagers this behavior is tolerated to some extent, but when losses reach a critical mass, their views change. “Although crocodilians are sometimes called living dinosaurs or living fossils, they are extremely intelligent and can easily learn to find easy prey,” he said.

Lake fishing in Nepal.
Lake fishing in Nepal. In Nepal’s lakes and rivers, there is conflict between fishing communities and poachers over fish stocks. Image by Neil Palmer/IWMI/Bioversity International via Flickr (CC BY-NC-ND 2.0).

“This could increase human-crocodile conflict in the area,” said study co-author Santosh Bhattarai.

At the same time, the reserve does not compensate the villagers for the fish eaten by the bandits. Such schemes already exist for cattle killed by tigers and leopards and crops damaged by elephants.

Chief Warden of Koshi Tappu Wildlife Sanctuary Ramesh Kumar Yadav said it is difficult to calculate how many fish a poacher eats in the pond, let alone compensate for the loss.

Santosh Bhattarai said it may be too early to draw broad conclusions as longer-term data and in-depth studies are needed to determine the extent of this movement of pirates away from the Koshi River and towards fish farms. “But we can say with certainty that it has something to do with this issue [declining] there is a stock of fish in the river,” he added.

Competition with relatives

As pirates and humans alike find it increasingly difficult to find fish in the river, another predator has entered the picture, putting more pressure on an already dwindling resource. In February of this year, the Nepalese government released 20 gharials (17 females and three males) raised in captivity into the Koshi River. Known for its distinctive slender nose ending in a comical bulbous snout, the gharial feeds almost exclusively on fish.

“This is a matter of great concern,” said Santosh Bhattarai. “We see that vulnerable pirates are not getting enough fish. But officials have introduced gharials, an endangered habitat-food breeding specialist, to the river.

A thief on the river bank.
A thief on the river bank. The marauders now share their habitat with the introduced gharials in some parts. Photo by Maureen Barlin via Flickr (CC BY-NC-ND 2.0).

A 2018 study of the coexistence of bandits and garis in India’s Katarniaghat Wildlife Sanctuary, near the border with Nepal, suggests that the two species are good at sharing habitat resources. But limited fish stocks could strain their relationship, Bhattarai said.

Yadav, ranger, Koshi Tappu Wildlife Sanctuary, said the gharials were released into the Koshi river to create conservation awareness among local people.

“Until now, the flagship species of the reserve has been the wild buffalo [Bubalus arnee]. We want more species to be introduced so that the local community understands their value and takes steps to protect habitats such as rivers in the case of gharials,” he said.

Santosh Bhattrai said putting poachers in competition with gharials threatens to push an already vulnerable species closer to the edge. “It makes no sense for a sensitive species to compete with its endangered cousin.”

Banner image: Bandit crocodile in Chitwan National Park. Photo by Quintus Ragnvaldr via Flickr (CC BY-NC-SA 2.0).


Bhattarai, D., Lamichhane, S., Pandeya, P., Bhattarai, S., Gautam, J., Kandel, RC and Pokheral, CP (2022). Status, distribution and habitat use of the predatory crocodile (Crocodylus palustris) in and around Koshi Tappu Wildlife Sanctuary, Nepal. hellion, 8(8).doi: 10.1016/j.helion.2022.e10235

Choudhary, S., Choudhury, BC and Gopi, GV (2018). Spatial-temporal partitioning between two sympatric crocodiles (Gavialis gangeticus & Crocodylus palustris) in Katarniaghat Wildlife Sanctuary, India. Protection of the aquatic environment: marine and freshwater ecosystems, 28(5), 1067-1076. doi: 10.1002/aqc.2911

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Animals, Conflict, Conservation, Endangered Species, Environment, Environmental Law, Fish, Fisheries, Freshwater Animals, Freshwater Ecosystems, Habitat, Habitat Loss, Herps, Human-Wildlife Conflict, Overfishing , Reptiles, Rivers, Wildlife, Wildlife

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