This enchanting display is due to the annual butterfly migration that starts with the onset of the southwest monsoon; butterflies migrate from the Western Ghats to the Eastern Ghats.
Published May 31, 2025 | 8:00 AM ⚊ Updated May 31, 2025 | 8:00 AM
A flock of butterflies on a tree. (Arun Urs)
Synopsis: With the onset of the southwest monsoon, butterflies from the Western Ghats started their migration to the Eastern Ghats. Since Bengaluru is on the migration route, it offers the residents a magnificent view.
For the past few weeks, Bengaluru has been spotting flutters of butterflies high in the skies. Many residents have shared videos of this magnificent spectacle on social media.
This enchanting display is due to the annual butterfly migration that starts with the onset of the southwest monsoon; butterflies migrate from the Western Ghats to the Eastern Ghats.
The species that are most seen during this migration include the Blue Tiger (Tirumala limniace), Dark Blue Tiger (Tirumala septentrionis), Common Crow (Euploea core), and Double-banded Crow (Euploea sylvester).
A flock of butterflies on a tree. (Arun Urs)
“This year appears to be a good migration year, since large numbers (of butterflies) are observed — likely due to the strong monsoon rains in the Western Ghats,” Nithin Ravikanthachari, a trained naturalist and post-doctoral research associate at the University of Montana, told South First.
He noted that this year, the migration has begun earlier than expected, likely due to the early onset of the monsoon.
Since this migration is triggered by the onset of the southwest monsoon, its timing can vary from year to year. The butterflies typically begin aggregating in the Western Ghats just before the monsoon arrives. While we do not know the exact cues that trigger this aggregation, they might be responding to subtle environmental changes such as shifts in temperature, humidity, or atmospheric pressure,” Ravikanthachari said.
“So, if the monsoon arrives early, the migration is likely to follow suit. The strength of the monsoon also influences how many butterflies migrate—we tend to see larger numbers during strong monsoon years,” he added.
The butterfly migration in South India spans around 1,200-1,500 km.
Naturalists Arun Kumar Raj Urs, Narmatha Urs and Swathi HA have been noting the migration for the past 10 years and have successfully mapped a few of the migration routes.
A flock of butterflies on a tree. (Arun Urs)
According to a study by Arun, the migration of butterflies from the Western Ghats begins from somewhere near Sringeri, continues to Kukke Subramanya, and moves onward to Madikeri (Mercara).
One group in great numbers then divert towards Hassan. And another group makes their way through the Brahmagiri Hills from Madikeri heading towards Wayanad and the forests of Nagarahole National Park, the Nilgiri hills and onward to the Anamalai Hills and Coimbatore.
Some choose a different path through the forests of Nagarahole National Park and Bandipur Tiger Reserve, reaching Biligirirangana Tiger Reserve (BR Hills).
Butterflies taking the Hassan route pass through the outskirts of Bangalore in places like Savandurga, Ramanagara, Kanakapura, Mekedatu and pass the Male Mahadeshwara Hills and into Yercaud in the Salem district of Tamil Nadu. Since the lifespan of butterflies is only around 30 days, it might be the second or, sometimes, the third generation which reaches their destination.
The reverse migration happens with the receding of the southwest monsoons and the onset of the northeast monsoons. Researchers noted that, over the years, whenever there is a rain deficit during the monsoon, the migration is quite meagre — an impact of climate change.
The study by Arun said that migration is important since butterflies are the second largest “pollinators” after bees. If the migration of these two species doesn’t occur, it will have a direct impact on the vegetation around us, noted experts.
They said even animals higher up in the food chain, like tigers, or large ones like elephants, wouldn’t survive for long without these two pollinators, due to their critical role in maintaining ecosystems.
(Edited by Muhammed Fazil.)
