Researchers tag milkweed butterflies to understand migration behaviour, seek help in monitoring

Discover the fascinating migration patterns of butterflies in India and how researchers are tracking them for valuable data.

Everyone looks forward to the monsoon for relief from a torrid spell of heat. But lepidopterists or butterfly enthusiasts of the southern parts of our country await rain for an entirely different reason. Close to the start of the southwest monsoon in Kerala, butterflies of some species migrate en masse from the Western Ghats to the Eastern Ghats and plains.

Initially it was believed that rain in the Western and Eastern Ghats drove the butterflies to migrate from Kerala to Tamil Nadu and vice versa. But researchers believe that it could be one of the factors.

“Every species has its own host plants and based on their availability, it tends to migrate,” says P.A. Vinayan, a research assistant at KREA University.

While certain species receive more attention than others in the realm of butterflies, many lesser-known species have intriguing mysteries of their own. In order to monitor these migrating butterflies and study them, Mr. Vinayan, along with his adviser Shivani Jadeja at KREA University, and a few other researchers followed a non-invasive approach that was modeled and used for a successful tagging technique done on monarch butterflies in the United States.

The nomadic tendency of these butterflies makes it imperative to tag a large number in order to guarantee adequate recoveries for useful data. Their team tagged the migratory milkweed butterflies, namely Blue Tigers and Crows, in Wayanad, Kerala, before the monsoon to track their migratory movements.

According to Mr. Vinayan, the first step in the non-aggressive procedure is capturing, which calls for the use of nets. This is followed by tagging, in which every butterfly is given a small circular sticker tag that is applied to the discal cell on the ventral surface of the right hindwing. They bear unique identification numbers. Then comes the process of recording, done with the date of tagging, the tagger’s name, tag number, release location, butterfly’s sex, and wing condition. And eventually they are released. 

After being handled with extreme caution to prevent injury to their wings, the butterflies are released in two minutes at the exact spot where they were caught.