Tracking an invasive species: Giant African Land Snails in Mongar

2026-03-09 - 09:14

The Giant African Land Snail (Achatina fulica) infestation, first detected in Gyalpozhing, Mongar in 2008, continues to affect communities in eastern Bhutan, with the invasive species now established in Lingmethang and surrounding areas. Saling Mangmi Tshering Norbu said, “When the Giant African Land Snail first emerged in Gyalpozhing in 2008, it wreaked havoc everywhere it went. Some of the farmers even had to abandon their farms.” According to the Mangmi, the snails were initially confined to Gyalpozhing but gradually spread over the years. He said, “Now, the snails have reached till Lingmethang and are prominent there during May to September.” At the Regional Poultry and Pig Breeding Center and the Agriculture Research Center in Lingmethang, staff follow a seasonal schedule to manage the snails. Based on the timing of the snail’s arrival during the hot months, traps are set, and snails are collected and disposed of accordingly. The Mangmi said that warm and humid sub-tropical and temperate conditions favor the snails’ emergence from the soil. He said that officials from the Bhutan Food and Drug Authority (BFDA) in Mongar monitor the snail population during these months. In 2025, BFDA officials conducted public awareness campaigns and capacity-building programs to control the invasive species. Farmers and residents in affected areas said the infestation had disrupted daily activities. Nima, a farmer from Gyalpozhing, said it was once difficult for people to maintain kitchen gardens outside their homes. “Last year, we were taught to make traps for the snails,” he said. He explained that residents were instructed to cut small windows into five-litre oil containers, place whey inside instead of water, and bury the container partially underground. The snails are attracted to the smell of whey and become trapped inside, where they die. Tsheltrim Dorji, a taxi driver in Mongar, said, “All the tenants in our building have set the trap during the snail season here.” Tshering Dema, a shopkeeper in Lingmethang, said the snails are particularly visible during the rainy season. “During the rainy season, the snails are scattered all over the ground like pebbles, and they get crashed by vehicles and left to decay, emitting a foul smell,” she said. She said that the snails were not previously present in Lingmethang and arrived a few years after the initial emergence in Gyalpozhing. The Department of Environment and Climate Change (DECC) is implementing a comprehensive control strategy, which includes manual collection and safe destruction of snails and eggs, trapping systems developed through the project, habitat management, sanitation improvement, public awareness campaigns, quarantine and movement control measures, and capacity building of field staff and local leaders. The Saling Mangmi said the infestation has decreased due to combined efforts by communities and authorities. However, he expressed concern about further spread. He said, “Places like Khalangsi, Lingmethang, Gyalpozhing, Jangdung have already been infested with the snail. If we do not take measures to prevent the spread of this snail, then there are high chances that the snail will spread to other places.” According to BFDA, since the detection of Giant African Land Snails in 2008, they have initiated domestic quarantine measures in Gyalpozhing and Lingmethang in Mongar to prevent further spread. Every year from May to September, officials conduct monitoring and inspection. Public awareness activities include installing biosecurity signage at strategic points and distributing brochures outlining the risks associated with the snail and actions to take if it is sighted. The Giant African Land Snail thrives in tropical and subtropical climates characterised by high humidity and warm temperatures. After a drop to 14.1°C in 2018, the average temperature during October, November and December has increased steadily by an average of 0.3°C in Bhutan. This trend aligns with findings from the Climate Change Projection Report 2024, which forecasts an increase in both maximum and minimum temperatures across Bhutan in the coming decades. The report attributes the projected changes to increased greenhouse gas emissions and outlines warming scenarios under moderate and high emission pathways. It also notes that pre-existing vulnerabilities may complicate adaptation efforts, particularly in sectors such as agriculture, hydropower, water supply and construction. According to the report, precipitation is expected to decrease in the medium term but increase in the long term. Northern, western, north-western and south-western Bhutan are projected to experience higher precipitation, increasing the risk of floods. By the end of the century, all dzongkhags are expected to see an increase of at least 56 millimetres in total annual precipitation compared to the baseline. Additionally, 2024 was recorded as the warmest year on record after an extended period of exceptionally high monthly global mean temperatures, according to the World Meteorological Organization. The Department of Environment and Climate Change said that the infestation of the Giant African Land Snail in Lingmithang and Gyelpozhing in Mongar remains a significant environmental and biosecurity concern. Since the initial start of the project funded by the Adaptation Fund and implemented by DECC and BFDA, the population has reduced. Improved surveillance, awareness, and coordinated response efforts by DECC, BFDA and partner agencies have resulted in better containment and localized population reductions. While eradication has not yet been achieved, the situation is now more systematically managed. This story was produced as part of the media reporting grant funded through the Australian Government’s Regional Media Support Fund through JAB.