- A widely held misperception of the threat it poses and changes to its habitat are threatening the existence of the Sri Lankan keelback, a mildly venomous snake that inhabits the island’s southwest, new research says.
- The expansion of agriculture and infrastructure development in rural areas is contributing to the loss and fragmentation of the species’ habitat.
- Researchers have called for further study into the keelback to achieve a better conservation assessment of the species, which in turn can inform national policies to ensure its survival.
A general fear of snakes, lack of understanding of reptile behavior, and human encroachment into wilderness areas are putting increasing pressure on a unique snake species found only in Sri Lanka, a new study shows.
In a paper published in Vertebrate Zoology after 11 years of field study of the Sri Lankan keelback (Balanophis Ceylonensis), also known as the blossom krait, researchers say the public’s fear and misunderstanding have led to people attacking and killing non-venomous and mildly venomous snakes.
The keelback, like many rear-fanged snakes, is only mildly venomous, but is often perceived as being highly venomous. It’s a fear that’s widely held with regard to snakes in general in Sri Lanka, which for the most part are semi to mildly venomous.
Contributing to this fear is Sri Lanka’s high snake-bite mortality rate, exacerbated by lack of access to adequate health care, particularly in rural areas where people are more likely to encounter snakes.
Keelbacks in particular prefer forest areas with dense, mature canopy and microhabitats that provide shelter, such as decaying moist leaf litter and coarse, woody debris.
But with the expansion of agriculture and infrastructure development in Sri Lanka’s rural southwest, there is increased habitat loss and forest fragmentation. Urbanization and increasing human settlements also contribute to habitat loss.
According to Suranjan Karunarathna, a herpetologist and corresponding author of the new paper, this trend threatens the survival of the species, as its habitat undergoes rapid changes. “This also results in more road kills,” he said of the snakes flushed out of the forests as a result of fragmentation and habitat loss.
“The current populations of these snakes are severely fragmented,” the paper says. “Deforestation and degradation of small forest patches where they live are now causing a decline in both the area of occupancy and the extent of occurrence.”
Considered endangered in Sri Lanka and near threatened in the IUCN Red List, the keelback today occurs in a range spanning just over 1,600 square kilometers (620 square miles), known as its area of occupancy.
“The core area of the lowland wet zone is the best habitat for them, where the probability of occurrence is high,” Karunarathna said. “Then, the wet zone periphery and the central massif support them.”
Previous research identified the species as being restricted to 23 locations, but the new paper recorded 15 more.
During their survey of 83 sites, the researchers recorded keelbacks in 25 locations, 10 of them previously known localities and 15 new sites. “We could not document the snake in 11 sites where the snake was previously recorded,” Karunarathna said.
The keelback has some unique traits: First, it’s a sluggish creature that’s mostly active during dusk. Second, it’s evolved a genetic resistance that enables it to ingest toxic prey. And perhaps most interestingly, it has the ability to play dead for well over 20 minutes, as a survival tactic.
“With a bias towards small vertebrate prey, keelback is an active forager and not a sit-and-wait predator,” said study co-author and prominent herpetologist Anslem de Silva. “Its prey selections are also influenced both by genetics and the season of the year.”
Researchers say the keelback’s secretive nature and its limited surface activity may contribute to the snake being considered somewhat of a rarity. This, in turn, confounds efforts to reach a scientific consensus on the species’ conservation status.
“There is a conservation disparity about this rare endemic snake with a restricted distribution within Sri Lanka. Nationally, it is considered endangered whereas the global assessment is near threatened,” the researchers said. This disparity, they said, throws into question “the actual conservation status and the actual rarity.”
“Disagreements between conservation assessments may also impede national conservation actions as well as policy decisions.” they said, calling for further studies into the keelback.
“There is a need for a consolidated scientific information base and informed conservation planning of this unique secretive snake,” Karunarathna said.
Gabadage, D., Surasinghe, T., De Silva, A., Somaweera, R., Madurapperuma, B., Madawala, M., & Karunarathna, S. (2018). Ecological and zoological study of endemic Sri Lankan keelback (Balanophis ceylonensis): with implications for its conservation. Vertebrate Zoology, 68(3), 225-236.
Banner image of a Sri Lankan keelback, an endemic snake primarily inhabiting the island’s southwest, courtesy of Suranjan Karunarathna.