- Declining fish stocks in Nepal’s Koshi River threaten the Mugger Crocodile, a species already under pressure from historic poaching and habitat loss.
- Crocodiles are increasingly encroaching on community-run fish farms in the buffer zone of Koshi Tappu Wildlife Sanctuary in search of food, a new study shows, increasing the risk of conflict with humans.
- At the same time, they face competition from gharials, a predominantly pescatarian crocodile that is being reintroduced to the Koshi as part of a government-run conservation program.
- “Making a vulnerable species compete with its critically endangered cousin does not make sense,” said one of the study’s authors.
KATHMANDU – They can dig burrows during extreme weather events, run on land, and eat just about anything. These and other traits make aggressor crocodiles (Crocodylus palustris) a versatile species capable of adapting to change.
“As part of the study, we conducted a pester count in the reserve and its buffer zone, where households and communities manage private fish ponds supported by the wildlife reserve,” said lead author Divya Bhattrai. of study and researcher in Nepal. University of Agriculture and Forestry. “We also assessed the threats the attackers face in their habitat.”
Koshi Tappu’s survey was conducted during the Nepalese winter, from mid-September to mid-December 2020, when the attackers come out to bask in the sun and are easier to spot. Bhattarai and his team observed 35 attackers, up from 16 recorded in 2013. “The number may have increased as we inspected not only the protected area, but also the private and community ponds in the adjacent buffer zone,” he said. she declared. Of the 35 individuals recorded, 19 were seen in the buffer zone next to community and private fish ponds.
While easy picking at fish farms may attract crocodiles to villages, other factors also keep them away from the river, researchers say. According to the study, the wildlife sanctuary issued 466 permits to indigenous communities to fish in a small stretch of the river. But many license holders have been found to fish more than their allocated quota, and many unlicensed fishers also operate in the area. “Fishermen have told us that their yields have also gone down in recent years,” Bhattarai said.
The researchers also found that the attackers rarely appeared threatened when moving among humans living near their habitats. Their distribution was little affected by human disturbance, distance to human settlements or even roads. “We discovered that one of the communities worshiped the abusers as their primary deity,” Bhattarai said.
This means the attackers have largely been given free rein to roam the fish ponds at any time. For most villagers, this behavior is tolerated to some extent, but when losses reach critical mass, they change their minds, said conservationist Ashish Bashyal, a member of IUCN’s Crocodile Specialist Group, who did not participate in the survey. “Although crocodiles are sometimes called living dinosaurs or living fossils, they are extremely intelligent and can easily learn to find easy prey,” he added.
“This has the potential to increase human-crocodile conflict in the region,” said study co-author Santosh Bhattarai.
At the same time, the wildlife sanctuary does not compensate the villagers for their fish eaten by the aggressors. Such programs already exist for livestock killed by tigers and leopards, and for crops damaged by elephants.
Ramesh Kumar Yadav, chief warden of the Koshi Tappu Wildlife Sanctuary, said it was difficult to quantify how many fish an attacker may have eaten from a pond, let alone provide compensation for the loss.
Santosh Bhattarai said it may be too early to draw general conclusions, as longer-term data and in-depth studies are needed to determine the extent of this movement of aggressors away from the Koshi River and towards the fish farms. “But we can say with certainty that it has something to do with the [declining] fish stocks in the river,” he added.
Competition with cousins
Even as aggressors and humans find it increasingly difficult to find fish in the river, another predator has entered the scene, putting even more pressure on an already dwindling resource. In February this year, the Nepalese government released 20 captive-bred gharials (17 females and three males) into the Koshi River. Known for its distinctly slender snout that ends in a comically bulbous nose, the gharial feeds almost exclusively on fish.
“It is a matter of great concern,” said Santosh Bhattarai. “We find that vulnerable aggressors are not getting enough fish. But the authorities have introduced the critically endangered habitat, food and breeding gharials into the river.
A 2018 study of the coexistence of muggers and gharials in India’s Katarniaghat Wildlife Sanctuary, near the border with Nepal, suggests that the two species are good at sharing habitat resources. But the limited availability of fish stocks could strain their relationship, Bhattarai said.
Yadav, the warden of the Koshi Tappu Wildlife Sanctuary, said the gharials were released into the Koshi River to raise awareness about conservation.
“The flagship species of the reserve has until now been the wild water buffalo [Bubalus arnee]. We want more species to be introduced so that the local community understands their value and takes action for the conservation of their habitats such as rivers in the case of gharials,” he said.
But putting aggressors in competition with gharials threatens to push an already vulnerable species closer to the edge, said Santosh Bhattrai. “Making a vulnerable species compete with its critically endangered cousin makes no sense.”
Banner image: Mugger crocodile in Chitwan National Park. Image 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 by the aggressor crocodile (Crocodylus palustris) in and around Koshi Tappu Wildlife Sanctuary, Nepal. Heliyon, 8(8). doi:10.1016/j.heliyon.2022.e10235
Choudhary, S., Choudhury, BC and Gopi, GV (2018). Spatio‐temporal partitioning between two sympatric crocodilians (Gavialis gangeticus & Crocodylus palustris) in Katarniaghat Wildlife Sanctuary, India. Aquatic conservation: marine and freshwater ecosystems, 28(5), 1067-1076. doi:10.1002/aqc.2911
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