Butterflies migrate in large numbers to Western Ghats in Tamil Nadu

Owing to good rainfall, there was heavy movement of butterflies of the Danainae sub-family from the Eastern Ghats, unlike last year

Tamil Nadu witnessed large-scale migration of butterflies belonging to the Danainae sub-family from the Eastern Ghats and plains towards the Western Ghats during September, as against the below-par movement during the same season last year.

Butterflies of the Danainae sub-family, such as Blue Tiger, Dark Blue Tiger, Double-branded Crow, and Common Crow, are known to migrate from the Eastern Ghats and plains towards various nearest hill ranges of the Western Ghats before the start of northeast monsoon.

During April and May, these butterflies, generally called ‘tigers and crows’ migrate from the Western Ghat hill ranges towards the Eastern Ghats and plains of Tamil Nadu, before the onset of the southwest monsoon.

Members of The Nature and Butterfly Society (TNBS), who have been monitoring the migration pattern since 2013, said ‘tigers and crows’ emerged in large numbers from the hills of Yercaud and surroundings in the Eastern Ghats during the last week of September. TNBS member V. Muthukrishnan said their movement from the Yercaud hills towards Salem started on a large scale on September 27 and it peaked on September 28.

According to M. Elavarasan, who tracked the movement in Salem, there was heavy migration on September 28 and it continued the next day.

Their southwest movement, towards the arc of hills in the Western Ghats between the Anamalai Tiger Reserve and the Nilgiris, was tracked from the Sathyamangalam hills in Erode, Tiruppur and Coimbatore. The migration started around 8 a.m. and continued till the evening. Observers said the migrating butterflies moved at a rate ranging between 10 to 200 individuals per minute over a short observation band width of 50 metres.

Wildlife biologist D. Boominathan observed their movement in the areas of the Sathyamangalam Tiger Reserve, especially near Vilamundi and over Dimbam hill ranges. According to TNBS member S. Gopalakrishnan, heavy migration was noted in the skies of Tiruppur on September 28 and 29.

The Coimbatore Forest Division became the largest beneficiary of the migration as the groups landed in various parts of the district on September 29 and 30. TNBS members H. Ramanasaran, Sravan Kumar, K. Sadheeskumar, J. Gayathri, and members of the Coimbatore Nature Society observed a huge southwest movement of butterflies in places including Sirumugai, Annur, Mettupalayam, Kunjappanai ghat road, Saravanampatti, Kavundampalayam, Saibaba Colony, Singanallur, Chettipalayam, Peelamedu, Vadavalli and Anaikatti.

A. Pavendhan, senior member of the TNBS, said the large-scale movement could be attributed to good rainfall during the just-concluding southwest monsoon season. Deficit rain during the southwest monsoon and subsequent northeast monsoon until November last year in the breeding areas of ‘tigers and crows’, namely Salem, Namakkal and Kallakurichi districts, could have resulted in poor migration in 2023.

During August 2024, Yercaud hills received many bouts of heavy rain of more than 8 cm while Salem district received 111% over the normal rainfall. Namakkal and Kallakurichi received above-normal rainfall of 48% and 40% respectively.

TNBS members observed the migration in the Nilgiris, Krishnagiri, Hosur, Kanniyakumari, Dindigul and Madurai. Other butterflies that were part of this migration included Lemon Pansy, Tawny Coster, Common Emigrant and Chocolate Pansy.

Published - October 04, 2024 10:26 pm IST