Every year, hundreds of butterfly species migrate around the world. Butterflies usually show multi-generational migration and in many cases, they don’t migrate in a swarm, which is atypical to vertebrate migration. As a consequence, when some butterflies fly towards a particular direction after some irregular intervals (for example, 1-2 individuals in 1-2 minutes), or not in a regular swarm, most people hardly believe they are migrating! Well, I was not an exception before starting my doctoral research on the causes and consequences of global butterfly migration. [If you are interested to learn more on how migration differ between animal groups, please read this paper]
In my three years of butterfly research in Bangladesh, I never observed the migration of any animal. One day, during our regularly scheduled meeting, I shared this with one of my Ph.D. advisors, Myron Zalucki, who is one of the best in this field. Myron mentioned, I either did not notice just because not migrating in a large swarm, or would soon going to observe one. I never expected to experience this soon!
It was 26th November, a sunny day. Just after completing my lunch, the unusual movement of some white butterflies dragged my concentration to look further at the Goddard rooftop. Several butterflies were flying in the same direction over the rooftop which continued for a few minutes. I could not resist myself but to inspect further and observed nearly 4-5 white butterflies were flying in a group (80-100 butterflies per minute) from the North-West to the South-East/South direction. It continued for more than an hour (2.30-3.45 PM) and after that, only a few of them were moving in that direction. Although most individuals were Belenois java, there were a few Danaus plexippus, Graphium sarpedon, some Catopsilia and some Lycaenids. I even borrowed an insect net from the Walter Lab but when I returned, the sun was down and only a few individuals were flying in that direction and a bit far away from the rooftop.
Surprisingly, some were returning in the opposite direction but most of those seemed old individuals (faded color), the reason is still unknown to me. Moreover, when the Archaeology building or the Biological Sciences Building were on their way, they did not change their direction but flew above these building, which is a common character of the butterfly migrants. It’s good to know that when obstacles appear, migratory butterflies do not change their direction but the non-migrants do. Interestingly, I observed similar occurrences several days but there were only a few of them, although they were moving in the same direction.
Experiencing something for the first time gives us inner pleasure and when it becomes your dream topic, the feeling is massive!
