- Sri Lanka is among the countries most vulnerable to climate change, with long drought spells, receiving intense rain during a shorter period with a marked increase in flood events.
- During flooding, crocodiles inhabiting rivers tend to reach land and move closer to human settlements, increasing the risk of encounters with people.
- The Nilwala River flows through southern Sri Lanka and recent flood events have increased croc encounters with humans in the Matara district and escalated threats to human safety, resulting in disaster management responses.
- During recent flooding events, no serious incidents linked to crocodiles were reported, but wildlife officials had to chase crocs away from riverbanks, highlighting the need for an immediate and durable solution for the human-crocodile conflict around the Nilwala River area.
MATARA, Sri Lanka — Flying birds, running squirrels, hopping hares and snakes are species that frequent the tea estates in Akuressa in southern Sri Lanka. But an unusual heavy rustling and crawling sound of an animal disturbed a woman plucking tea, who let out a loud scream as she realized it was a giant crocodile next to her. She ran toward others, and the villagers caught this 15-foot-long giant after a difficult and risky operation.
Tea plantations are not considered the habitat of saltwater crocodiles (Crocodylus porosus), but there was severe rain in the area and the nearby Nilwala River began to flood. The crocodile likely reached the edge of the flooded area and got trapped in the tea plot as the flooding receded, said Priyanath Sanjeewa, a Matara district wildlife ranger.
The tea estate incident happened during the 2017 floods, but similar incidents where crocodiles ended up in areas that humans inhabit remain a common occurrence when the Nilwala River floods. The river also accounts for the country’s worst human-crocodile conflict, Sanjeewa said.
In 2016, when the river flooding intensified, one of the largest Nilwala River crocs moved to the edge of a nearby village named Weraduwa.
“On a number of occasions, crocodiles were found trapped inside buildings or home gardens as the water receded. So, we make it a point to warn people who leave their homes temporarily due to flooding to be wary once they return home, as there could be lurking danger, the wildlife ranger said. As flooding reduces, some crocs end up in culverts, so it’s best not to get too close to them, Sanjeewa added.
During a severe flood event that occurred in October, crocodiles were spotted in several paddy fields and along slightly flooded roads, Sanjeewa told Mongabay. Crocodiles had also moved to small canals where the water was calmer than in the river.
There were posts on social media warning people about crocodiles and referring to an incident when a dog was snatched by a croc. Displaced when their homes were flooded, this was an additional worry to flood victims.
Crocodiles like calm waters, so they try to move away from rapid flows as in the case of heavy rain where the river becomes swift and murky, also bringing debris and logs that can bang against their bodies, said Anslem de Silva, top herpetologist and chair of the IUCN Crocodile Specialist Group of South Asia and Iran.
During a 2008 crocodile survey, de Silva and his team counted around 50 crocodiles in a 5-kilometer (3-mile) stretch of the Nilwala River.
Increasing flood events
“We were traveling by boat to make this count, but there was heavy rain that day. The team did not spot even a single crocodile,” de Silva recalls. The animals tend to come to land with the intention of avoiding the rapidly flowing floodwater. But although they come to human habitations, crocs will evade humans as much as possible, he added.
“During floods, crocs can seek refuge in temporary water holes and get trapped as water levels recede, a common scenario with the Nilwala River,” said Dinal Samarasinghe, a researcher who is currently conducting a study on crocodiles in the Nilwala River.
Samarasinghe and team were there during another intense flooding incident in 2015; he recalls that it was an endless column of water flowing downstream with no riverbanks visible on either side. Crocodiles prefer to stay on the edges, as the water’s speed may entrap them in temporary water holes.
Floods can also help crocs to relocate and find new areas more conducive for their survival. It is compliant with the laws of nature, which ensure the crocodile population is widespread.
However, the floods can prove bad for crocodiles, as flooding can easily destroy their nests. The female crocodile lays eggs inside a nest built close to the river or a water hole. A flood can destroy these nests; however, the timing of recent floods was good for crocs, as there weren’t any nesting females at the time. “All the nests were likely to have been hatched out at the time floods came,” Samarasinghe told Mongabay.
“The Nilwala River used to be a lifeline for people living in the tiny villages. But due to the increased threat of crocodile presence, people have stopped accessing forest resources,” said Malindu Gajadeera, a social activist living on the banks of the Nilwala River. “The frequency of floods and their intensity have increased. Naturally, the fear of crocodiles is an additional burden for the villagers who have to vacate their properties during floods,” Gajadeera said.
People from older generations used to swim in the river. And there is folklore about crocs in the river, as the Nilwala historically has had many crocodiles. But those who live along the Nilwala no long swim in the river due to the fear of possible crocodile attacks, Gajadeera said, emphasizing the importance of swimming skills, specially during a flood.
Impact of climate change
Herpetologist Anslem de Silva also hails from Matara and had lived close to the Nilwala River for 23 years. He did not experience severe floods in those two decades but notes the flooding events have turned rather devastating and frequent in recent years. He said this river swelling could be the result of climate change, and such natural disasters would impact all animals.
“It is evident that climate change and natural disasters have increased worldwide in the past few years,” de Silva said.
A fear of crocs is not unique to the Nilwala range. In March, Australians were warned against crocs during severe floods in Queensland. When Hurricane Ida ripped through the U.S. in 2021, a man was killed by a crocodile while swimming in the floodwaters in New Orleans. In another incident, 70 crocodiles escaped from a crocodile farm during intense floods in southern China in September 2022.
There are 24 crocodile species in the world, but only eight species are known to attack humans. Sri Lanka is home to two crocodile species — the Mugger crocodile (Crocodylus palustris) and the saltwater crocodile. The mugger crocodile, too, tends to end up in human settlements, as it has the habit of moving around when its water holes are drying out, Samarasinghe told Mongabay.
Banner image: A saltwater crocodile (Crocodylus porosus), the largest living reptile in Sri Lanka, is now involved in more conflicts with humans. Image courtesy of Dinal Samarasinghe.
Samarasinghe, Dinal J S. (2014). The Human-Crocodile Conflict in Nilwala River, Matara (Phase 1). 10.13140/2.1.3502.1448.