Swallowtail butterflies in key Assam habitat face a citrus worry Premium

The overexploitation of 25 species of host plants valued for their medicinal properties has affected swallowtail butterflies in forests on the Brahmaputra’s northern bank.

The overexploitation of 25 species of host plants valued for their medicinal properties threatens the swallowtail butterflies in the forest habitats of a part of Assam often referred to as the “citrus belt of the world”, a new study has found.

The study, conducted in the Bodoland Territorial Region on the northern bank of the Brahmaputra River, also underscored illegal cattle farming within the protected areas, agriculture and tea cultivation near the habitats, illegal tree felling, and pesticide use to be among the crucial factors contributing to the decline in the number of these butterflies.

Kushal Choudhury of Bodoland University’s Department of Zoology is the author of the study, which was published in the Journal of Threatened Taxa.

“The decline of swallowtail butterflies in forest habitats, which was not a major concern about two decades ago, made the International Union for Conservation of Nature mark them as globally endangered,” he said.

India hosts 77 of the 573 swallowtail butterfly species recorded across the world so far. The International Union for Conservation of Nature designated the northeastern part of the country, where 69 species have been recorded, a ‘swallowtail-rich zone’ under the Swallowtail Conservation Action Plan.

Dr. Choudhury’s study documented 4,267 individuals belonging to 35 species representing eight genera. Three are endemic to the region while 12 enjoy federal protection.

“Butterflies are valuable indicators of the environment, whose health can influence their presence, abundance, and diversity. The findings suggest that the studied landscape [in the Bodoland Territorial region] is crucial in supporting larval host plants, adult resources of swallowtail butterflies, and other abiotic factors,” he said.