Have you noticed this butterfly which is seen almost everywhere in Bangalore? They are fluttering all over the city – these butterflies are a part of the migratory swarm. Hundreds of butterflies are found roosting on trees and plants, it is magical indeed to observe this visual treat.
Lepidoptera migration is a biological phenomenon whereby populations of butterflies or moths migrate over long distances to areas where they cannot settle for long periods of time. By migrating, Lepidoptera species can avoid unfavorable circumstances, including weather, food shortage or over-population. The Danaids in South India are also prominent migrators, between Eastern Ghats and Western Ghats. Three species are involved in this, namely Tirumala septentrionis, Euploea core and Euploea sylvester. Sometimes they are joined by Lemon Pansy (Junonia lemonias), Common Emigrant (Catopsilia pomona), Tawny coster (Acraea terpsicore) and Blue Tiger (Tirumala limniace). They cross Bangalore on their way to the Eastern ghats.
- During March to May the direction of migration is SW-NE i.e from the Western ghats to the Eastern ghats.
- During Sept to November the direction of migration is from NE to SW i.e from the Eastern ghats to the Western ghats.
- The distance covered is about 350-500 kms
The migratory swarms typically consist of several million, perhaps tens of million, butterflies. This annual migration is remarkable for two reasons. First, it seems to take place in response to the torrential monsoon rains in the Sahyadri. This is in contrast to most well-known migrations, which usually take place in response to cold or droughts. Second, this migration is longitudinal (east-west), not latitudinal (north-south) or altitudinal like most other well-known migrations. This is presumably because of the monsoonal patterns in peninsular India. For more info
These butterflies roost on trees and shrubs, they are migratory pollinators so they form an important part of our ecosystem. So we should focus on extensive public outreach programs to increase awareness and appreciation of this migration as well as encourage participation in conservation efforts. Promotion of nectar plants along roadsides, neighborhoods, parks, gardens and public lands in the migratory corridors is important to preserve this migration. Citizens can watch these butterflies by planting nectar rich plant species around their neighborhoods.
The Monarch butterflies fly thousands of miles southward each year to their wintering grounds in Mexico. But human development is shrinking those wintering grounds and climate change is impacting the plants they feed and roost upon.
Biologists have long been fascinated by the innate and learned behaviors underlying animal migrations. When monarchs are breeding, for instance, they can live up to four weeks, but when they are migrating, they can live as long as six months.
Photo credits :Kannan.A.S