Studies on migration patterns of milkweed butterflies and their feeding habits can help protect them, say researchers

Milkweed butterflies migrate westward from the Eastern Ghats and plains to the Western Ghats, becoming active for more than two months upon their arrival

(From left) Striped tiger, Blue tiger and Dark blue tiger. Photo: Special Arrangement

Millions of Milkweed butterflies undertake a migration between the Eastern and Western Ghats in southern India, seeking refuge from the harsh summer.

This spectacular ecological phenomenon had been recorded more than a century ago but received little research and conservation attention until recently. However, a recent study by a team of researchers shed light on the migration patterns of Milkweed butterflies in southern India, which has the potential to contribute to the conservation of these butterflies and their migration in the face of ongoing changes in land use, habitat degradation, and climate warming.

The study was published in the recent issue of the Journal of Insect Conservation. After southwest monsoon, Milkweed butterflies migrate westward from the Eastern Ghats and plains to the Western Ghats, becoming active for more than two months upon their arrival.

Between October and April, most of the Milkweed butterflies in the Western Ghats congregate in large numbers at specific sites during winter and dry seasons. When the summer rain cools southern India, the butterflies migrate eastwards into the Eastern Ghats and the plains.

The studies reveal that the wings of the majority of butterflies during their eastward journey are battered than that in the westward migration. Also, the researchers found that the dominant species involved in the migration, Dark blue tiger and Double-branded crow, are not found breeding in the mid and high-altitude evergreen and semi-evergreen forests of the Western Ghats.

P.A. Vinayan, who led the study, says the adults of Dark blue tiger and Double-branded crow that arrived in the Western Ghats may be migrating reversely and breeding in the Eastern Ghats and the plains of southern India. However, further studies are needed to confirm the finding, says Mr. Vinayan, who is also the president of the Ferns Nature Conservation Society.

“The migration of Milkweed butterflies also plays a vital ecological role during the migration. As pollinators, their movements can impact entire ecosystems. Their migration is threatened by habitat destruction and climate change. Studying their migration patterns and feeding habits can impart the interconnectedness of plant and animal life. By unravelling the mysteries of their migration, we can help protect these beautiful creatures and the ecosystems they inhabit,” says Mr. Vinayan.

“The Ferns society has begun tagging these migrating butterflies. Our hope is that long-term monitoring of these tagged individuals will reveal more about the darker aspects of their migration,” he says.

M.A. Yedhumon, researcher, Wildlife Institute of India, Dehradun; M.R. Anoop, researcher, Ashoka Trust for Research in Ecology and the Environment, Bengaluru; and N.S. Sujin, researcher, The Sálim Ali Centre for Ornithology and Natural History, Comibatore; were the other members of the team.