Sitting on the wings of a butterfly

The first time I heard the term butterfly tagging, I was intrigued. I had heard of mammals and reptiles being tagged to help biologists understand their movements and behaviour, but what could one possibly attach to a butterfly? My mind conjured up strange images of butterflies sporting miniature collars on their abdomen, or some gizmo hoops on their wings. Thankfully, my wildly misplaced notions were soon going to be dispelled; I was attending a workshop on tagging monarch butterflies (Danaus plexippus).

It would be difficult to find a person who isn’t enamoured, at least for a moment, by seemingly weightless wings glittering in the sunlight. Butterflies have been a motif and symbol in various cultures dating back to more than 3000 years. The ancient Greek word for “butterfly” is ψυχή (psȳchē), which translates to “soul” or “mind”. Many Meso-American and Southeast Asian cultures believe butterflies to be reincarnations of the deceased, epitomising metamorphosis through its transition from a caterpillar to a winged creature.

Yet, despite their widespread popularity, butterflies are not as eternal as we would like them to be. In fact, they are dying in apocalyptic numbers along with other insects. A 2019 report in Biological Conservation mentions that 40 percent of all insect species are declining globally and one-third are critically endangered. Insects pollinate more than 8o percent of terrestrial plants and directly contribute to crop yields. Reducing the significance of an entire class of animals to their role in supporting human well-being is hardly justified, but even by these narrow parameters, the decline in insect populations should be of significant concern to us. It wouldn’t be a stretch to claim that entire food webs and ecosystems could collapse if the trends continue. The tragedy of losing creatures that have survived and evolved for millions of years is hard to imagine. 

These heavy thoughts were momentarily brushed aside by the graceful glide of a monarch butterfly, surfing the cool winds by the seaside where we had gathered to learn more about them. We were a motley group of nature enthusiasts and educators, united in our curiosity and fascination to better understand these enigmatic creatures. One of the most iconic pollinators among the North American butterflies, monarchs migrate annually across North and South America, making them the only known butterflies to embark on a two-way migration similar to birds. They are thought to have been given the name “monarch” in honour of King William III of England, as the butterfly’s predominant rusty-orange colour matches the king’s secondary title, ‘Prince of Orange’. “Can you believe that we’ll be seeing the great-grandchildren of these butterflies up north next year!” exclaimed our workshop host and naturalist, Kathy (name changed).

Unlike other butterflies that can withstand the winter as larvae, pupae, or even as adults in some species, monarchs cannot survive the cold winters of northern regions. Instead, every autumn, millions of monarch butterflies leave their summer breeding grounds in northeastern USA and Canada and travel more than 3,000 miles to reach overwintering grounds in southwestern Mexico. These ‘super generations’ of migrating monarchs are unique because though they are the same species, for reasons still unclear, they can survive for up to eight months, as compared to the much shorter lifespan of other monarch generations that do not migrate. Using air currents, they travel all the way back to Mexico—a feat as remarkable as it sounds. Some overwinter in southeastern and western parts of North America as well. 

Known as Mariposa Monarca in Mexico, the monarchs huddle together by the millions on the branches of oyamel fir trees found in the mountains of Central Mexico. The humid microclimate and densely packed arrangement ensure that the butterflies survive the cold. After waiting out the winter, they head part of the way back north to warmer climates such as Texas, where they mate and lay eggs on milkweed plants. The larvae subsist exclusively on milkweed plants, which contain toxins in the sap. The caterpillars are able to store the toxins, known as cardiac glycosides, in even higher concentrations than what is found in the plant, and carry them in adult form too. As a result, most birds attempting to make a meal of the monarch find them unpalatable or are forced to vomit soon after consumption. The bright orange stands for ‘Danger!’ it seems.

A monarch caterpillar on a milkweed plant afflicted with aphids
A demonstration of the way to hold a butterfly

“Their evolutionary defence has now become their weakest link though,” explains Kathy holding a milkweed cutting that had two caterpillars munching on its leaves hungrily. Increased use of herbicides and shrinking habitats have led to the milkweed plant population declining by 21 percent between 1995 and 2013. Almost mirroring the decline, the monarch population completing the winter migration dropped from 550 million in 2004 to a mere 33 million in 2013. 

Apart from the generation that makes the long haul and overwinters in Mexico, each generation lives for two to four weeks, mating, laying eggs, and dying, and the next generation continues the journey upwards. “When you look at this butterfly, you are witnessing a multi-generational saga that has been going on for millions of years. But, in just a few decades, rampant loss of habitat and host plant has put them in peril. So, with the help of organisations like Monarch Watch, we do what we can. Plant, hope, and tag,” adds Kathy.  

Founded in 1992, Monarch Watch is an outreach program focused on education, research, and conservation related to monarch butterflies. Through citizen science efforts, the organisation has encouraged the revival of native milkweed species and habitat restoration within backyards, schools, and parks. They also started the volunteer-driven tagging program by designing lightweight, circular tags with unique codes that can be attached to the butterflies in a specific manner such that the tags don’t interfere with their flight or harm them in any way. With over a quarter of a million tags distributed each year, meticulous data is received from volunteers who tag and release the butterflies after recording the tag code, tag date, gender of the butterfly, and geographic location. The efforts have helped answer critical questions about the pace and nature of the migration.

A tagged Monarch

As much fun as butterfly tagging might sound, carefully capturing the butterflies is an exercise in patience and perseverance. We also had to be careful to catch the right ones! In a classic case of animal mimicry, butterflies such as viceroy and Gulf fritillary share similar patterns and shades as the monarch. After nearly an hour of hunching, running, crouching, and jumping, we managed to capture only two with catching nets. Kathy explained how to hold the butterflies to ensure they are not hurt and slip them into a wax paper envelope so that all butterflies could be tagged in one session. 

While holding one, I was surprised to feel the strong, almost claw-like grip of its hind legs, which Kathy explained helps them cling on to the edges of flowers and plants. Kathy gently and expertly stuck a tag to the forewing and pointed to a black spot on a vein on each hindwing. “A male,” she said. The spots contain scales that produce volatile chemicals called pheromones used during courtship. Kathy spoke of volunteers who have been tagging the monarchs for over two decades, awaiting their annual presence with hope and concern. The long-term data has been especially useful to understand trends and even locate other overwintering habitats that were not known earlier. 

In India, similar citizen science projects have helped collect significant data about trees, birds, and plants. Consistent observation has often been the first step towards critical findings. For example, species of milkweed butterflies have been found to migrate between the Eastern and Western Ghats in southern India to escape the harsh summers.

After tagging the butterflies, we set them free, and they immediately took to the skies. Like winged messengers to a perilous and uncertain future, the monarchs seem to symbolise tenacity and resilience through their long journeys. In ensuring the continuity of their path and lifecycles, we can partake in some small measure, the wonder, beauty, and danger that the world continues to churn. 

Further Reading

Vinayan, P. A., M. A. Yathumon, N. S. Sujin, B. N. Kumar, P.A. Ajayan, P. K. Muneer and N. R. Anoop. 2023. Pattern and drivers of danaine butterfly migration in Southern India: implications for conservation. Journal of Insect Conservation 27(3): 505–516.

Zylstra, E. R., L. Ries, N. Neupane, S. P. Saunders, M. I. Ramírez, K. S. Oberhauser, M. T. Farr and E.F. Zipkin. 2021. Changes in climate drive recent monarch butterfly dynamics. Nature Ecology & Evolution 5(10): 1441–1452. doi.org/10.1038/s41559-021-01504-1 

Atlas Obscura. 2023. How Monarch Butterflies use the poison in milkweed plants. https://www.atlasobscura.com/articles/monarch-butterfly-poisonous-milkweed-science. Accessed on December 15. 2023.

Mongabay. 2019. Why are fewer monarch butterflies overwintering in Mexico? https://news.mongabay.com/2019/01/why-are-fewer-monarch-butterflies-overwintering-in-mexico/. Accessed on December 15. 2023.