The migration of butterflies from the hills of the Western Ghats to the planes of the Eastern Ghats via Coimbatore was less than what the region had witnessed in 2018.
Nature enthusiasts, who have been monitoring the movement of butterflies also found that the annual phenomenon did not take place in one of the seven traditional paths of migration in Coimbatore.
A. Pavendhan of Tamil Nadu Butterfly Society (TNBS) which has been tracking the annual migration for several years said that low levels of summer rain in the region could have affected the volume of migration.
“There was no migration reported in Coimbatore in 2016 when Tamil Nadu witnessed a drought-like situation. In 2017, the migration picked up. It was robust in 2018 when Coimbatore region received decent summer showers. With the movement strongly correlated with rain pattern, it is getting proven that butterflies are long-term indicators of weather,” he said.
The migration pattern has been observed as a cyclical movement. While the migration from the Western Ghats to the Eastern Ghats takes place before the onset of the South-West Monsoon, a reverse migration takes place before the onset of North-East Monsoon.
“This year’s migration via Coimbatore was observed between April 15 and May 30. Though the period band was longer, the movement of butterflies was less compared to 2018. There was no sustained movement of butterflies along the known broader migratory pathways in Coimbatore. While the migration lasted from 9 a.m. to 3 p.m. on several days last year, the movement was barely two to three hours in the morning this year,” said Mr. Pavendhan.
Regular paths
In Coimbatore, there are regular migratory paths of butterflies namely the Anamalai hills, Palakkad pass via Walayar, Siruvani hills, Marudamalai hills, Anaikatti hills and Kallar hills.
The observers of TNBS found that movement of butterflies along the migratory path from Siruvani hills to the east via Peelamedu and Singanallur did not take place this year.
Butterflies belonging to Danainae subfamily like Blue Tiger, Dark Blue Tiger, Double-branded Crow and Common Crow accounted for more than 90 % of butterflies found during the migration.
Movement of emigrant species like Common Emigrant and Mottled Emigrant were also reported this year.
To monitor butterfly migration at a larger level, various NGOs involved in butterfly studies formed a WhatsApp group called ‘Butterfly Migration India’ which has representation from almost all States.
“Butterflies are one of the indicator species as changes in the environment is closely reflected in their movement. Their movement is largely connected with the rain pattern. A larger and long term study is required to correlate their movement with the local and national weather system. ‘Butterfly Migration India’ was formed in 2016 to create a large data base from various NGOs across the country,” said Kalesh Sadasivan of Travancore Natural History Society who played a key role in forming the group.
The observers of TNBS found that movement of butterflies along the migratory path from Siruvani hills to the east via Peelamedu and Singanallur did not take place this year.
Butterflies belonging to Danainae subfamily like Blue Tiger, Dark Blue Tiger, Double-branded Crow and Common Crow accounted for more than 90 % of butterflies found during the migration. Movement of emigrant species like Common Emigrant and Mottled Emigrant were also reported this year.
To monitor butterfly migration at a larger level, various non-governmental organisations (NGOs) involved in butterfly studies formed a WhatsApp group called ‘Butterfly Migration India’ which has representation from almost all States.
Study needed
“Butterflies are one of the indicator species as changes in the environment is closely reflected in their movement. Their movement is largely connected with the rain pattern. A larger and long term study is required to correlate their movement with the local and national weather system. ‘Butterfly Migration India’ was formed in 2016 to create a large data base from various NGOs across the country,” said Kalesh Sadasivan of Travancore Natural History Society who played a key role in forming the group.