2016 ended on a sad note for nature lovers in Coimbatore, as the annual migration of butterflies to Western Ghats via Anaikatti hills did not take place even after January.
Scientists and researchers who are into the study of butterflies -- good bio-indicators of habitat quality and health -- attribute various reasons ranging from shortfall of North-East Monsoon to climate change as reasons.
The annual migration was being recorded from 2,000 according to nature lovers and scientists.
The migration to Anaikatti hills used to start from September which would continue up to December.
“The migration was comparatively less in 2015. One could not witness the phenomenon in 2016 too,” said Prabhakar V., a nature enthusiast who has been observing the pattern of butterfly migration at Anaikatty for years.
According to a study conducted by the Salim Ali Centre for Ornithology and Natural History at Anaikatty in 2012, the campus had witnessed mass diurnal migration (South-East to North-Eest) in November. The study found that the directional mass movement butterflies was around 300 m wide.
“According to a sampling study done by SACON, 4,09,780 butterflies crossed the campus on a peak day, on November 20, 2012. We could record ten species of butterflies in the sampling study. Though the migration used to happen via Anaikatty, we could not record their return via the same route,” said P. R. Arun, principal scientist and head of Environmental Impact Assessment division at SACON. Swarms of butterflies primarily included Blue Tiger, Common Crow, Common Emigrant, Plain Tiger, Common Leopard, Lemon Pansy, Danaid Egg Fly, Double Banded Crow, Dark Blue Tiger, and Lime Butterfly.
Mr. Arun felt that the reason for the migration required dedicated study before it came to an end. “We are yet to find the real reason for the migration as it is an environmental phenomenon. Even, they could have changed the path,” he added.
According to R. Eswaran, assistant professor, Department of Zoology with The Madura College, North-East Monsoon and the onset of winter in highly elevated areas could be a triggering factor for the migration.
“They migration used to witnessed in Pilloor valley, Kotagiri valley, and Kallar valley too. We could find traces of their return via Nilambur, Bandhipur and Muthumalai in March and May. While the migration is considered a downward journey on North-East direction, the return used to be an upward journey on South-West direction,” said Mr. Eswaran who had recorded the movement of the butterflies from hills of the Nilgiris to Velliangiri Hills via Anaikatty Hills in his Ph.D thesis.
