Hundreds of Danaine butterflies, also known as milkweed butterflies, have been tagged by a group of butterfly enthusiasts in Wayanad to track their migratory movement towards the eastern side of south India from the Western Ghats.
FERNS, a nature conservation society in Wayanad, has launched the programme as a part of a citizen science programme ‘Danaine Watch’ .
Every year, millions of Danaine butterflies undertake the journey in South India. Six species of milkweed butterflies have been found in the migratory swarms. It is believed that they fly from the Western Ghats to the Eastern Ghats and eastern plains during March and April, before the southwest monsoon.
The reverse migration happens before the northeast monsoon gains momentum in the Eastern Ghats, from September to November. This migration is believed to help the butterflies avoid heavy rains. An in-depth study on butterfly migration in the country is yet to be launched to know the secrets of the phenomenon.
Danaine Watch began in 2018 and, initially, volunteers followed the migrating butterflies on vehicles to track the mysterious routes. The endeavour revealed that the butterflies began their journey from the Western Ghats, reached the Erode forests, MM Hills Wildlife Sanctuary, and the Cauvery Wildlife Sanctuary in four days. Their further movement is still a mystery.
This year, hundreds of butterflies have been tagged from the Western Ghats to track their migratory movements. Butterfly tags are tiny stickers attached to the underside of one of the hind wings. Each tag will have a unique code. These codes will help track the origins of the tagged butterflies if they are recaptured.
The tagging has been completed before the onset of summer rains in the forest tracts of the Western Ghats when the butterflies start their eastward journey. Several teams of researchers, volunteers, students and forest staff joined in the tagging exercise.
“Milkweed butterflies are ideal candidates for citizen science projects in the country, for both practical and scientific reasons. From a practical perspective, the migrating milkweed butterfly swarms are impressive to the public because of their sheer numbers and colour. The effect the colourful swarms make in people’s minds will move them to invest time and contribute their observations. These valuable observations can help better understand their migration and in conserving butterfly populations. It is easy for laymen to locate these butterflies in their backyards as they are common butterflies that utilise habitats around habitations,” says M.A. Yathumon, coordinator of Danaine Watch.
Large-scale and long-term monitoring is required for a comprehensive understanding of butterfly migration. Over 600 butterflies belonging to six species, including Dark-blue tiger, Blue tiger, Glassy tiger, Double-branded crow, Common crow and Brown-king crow, have been tagged this year.
It is for the first time migrating butterflies are being tagged as part of a citizen science initiative in India, says P.A. Vinayan, researcher in charge of Danaine Watch. “Milkweed butterflies utilise diverse habitats in southern India during their annual migratory cycle, and their populations fluctuate dramatically between the years,” he says. “The numbers of butterflies in the congregations we monitor in the Western Ghats have drastically declined this season,” he says.
“The largest number of butterflies we ever recorded in a congregation was in 2019 when we counted over two lakh butterflies in the Begur range of the North Wayanad Forest Division. This year, we were able to find only less than 1,000 individuals at the same site,” he says.
“No butterfly congregations were sighted in the Aralam Wildlife Sanctuary, where many congregations have been reported in the past many years. Moreover, some regular sites were devoid of butterfly congregations in the Wayanad Wildlife sanctuary also,” he says.
“The maximum number of butterflies in a congregation we recorded this season was less than 5,000 individuals. It requires long-term monitoring of migrating butterflies to understand the population dynamics of the insects,” says Mr. Vinayan.
The team has requested help from citizen scientists to recapture the tagged butterflies and inform the details at the mobile number 9846704353.
