Large numbers of yellow and white butterflies have been spotted flying across several parts of Sri Lanka in recent days, attracting public attention and prompting questions about the unusual sight.
Videos and photographs circulating on social media show thousands of butterflies moving in groups, often in the same direction, in areas including Colombo, Galle and Ratnapura.
According to an explanation published by Fact Crescendo Sri Lanka, the phenomenon is a natural seasonal butterfly migration associated with monsoon rainfall, changes in vegetation and breeding patterns.
Experts say butterfly migrations typically occur during two periods in Sri Lanka, with the main migration taking place between October and December and a smaller movement occurring between March and April.
Rainfall during the monsoon transition encourages the growth of plants that provide food and breeding habitats for butterflies, leading to an increase in their populations.
As populations grow, butterflies move across different regions in search of suitable plants for laying eggs and to reduce competition for resources.
Among the species involved are the Lemon Emigrant, Mottled Emigrant, Lesser Albatross and Common Albatross butterflies.
A 2024 study published in the scientific journal Taprobanica, involving researchers including Professor Kapila Dissanayake of Sabaragamuwa University, identified major butterfly migration routes across Sri Lanka.
The study, which collected information from 60 locations, found that one of the main migration routes runs from the southeast towards the northwest.
Researchers observed movements from the Kumana National Park area towards Wilpattu, covering approximately 280 kilometres over three to four days.
The average flight speed of migrating Albatross butterflies was estimated at around 11 kilometres per hour.
Meanwhile, a former president of the Butterfly Conservation Society of Sri Lanka told Fact Crescendo that seasonal rainfall encourages the growth of host plants, particularly in the dry zone, creating favourable conditions for butterfly breeding.
She said the increased butterfly population subsequently spreads across the country, influenced by wind patterns and the availability of suitable plants.
The expert also reported personally observing Lemon Emigrant and Mottled Emigrant butterflies moving from east to west in the Borella area of Colombo.
- Are the butterflies heading towards Sri Pada?
The seasonal movement has also revived a traditional Sri Lankan belief that butterflies travel towards Sri Pada, also known as Butterfly Mountain.
Experts explain that some butterflies exhibit a behaviour known as hill-topping, in which they gather around elevated locations to find mating partners.
However, research indicates that many migrating butterflies travel northwest rather than specifically towards Sri Pada.
- Is the migration a warning of a natural disaster?
The widespread sightings have also prompted speculation that the movement could signal an approaching cyclone or another natural disaster.
However, experts say there is no established scientific evidence that mass butterfly migration predicts a major natural disaster.
While butterflies are sensitive to changes in atmospheric pressure, humidity, temperature and wind patterns, their movements cannot be treated as an official warning of an impending disaster.
Experts further note that climate change, irregular rainfall and the spread of invasive plant species pose growing threats to butterfly populations.
Despite the large numbers currently being observed, research suggests that butterfly populations and major migration events have declined compared with historical levels.
The current sightings are therefore considered part of a natural seasonal ecological cycle, rather than evidence of an impending disaster. (Newswire)
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