Millions of blue tiger and dark blue tiger butterflies are migrating from the Eastern Ghats towards the Western Ghats with the onset of the North-East monsoon.
The migrating butterflies include blue tiger (Tirumala limniace), dark blue tiger, common crow and double-banded crow butterflies, with large numbers recorded across Tamil Nadu and Kerala.
They migrate towards the Western Ghats to escape heavy North-East monsoon rains and reach forests with suitable host plants, where they feed, mate and lay eggs.
The next generations remain in Western Ghats forests during the following months and fly back towards the Eastern Ghats around May, ahead of the South-West monsoon.
Large congregations have been recorded in places such as Coimbatore, Salem, Erode, Tiruppur, Madurai, Silent Valley and Parambikulam, with citizen groups helping document the migration.