Nature has many miracles but this is one of my favour-ites. Many animals are known to migrate to keep warm in the winter, but imagine tiny, little, delicate winged butterflies making an unimaginable mig-ration of over 3,000 kms.
The Monarch starts its life as a tiny yellow, black and white caterpillar. This transformation from larvae to an adult butterfly is one of the most amazing in the animal world. The Monarch caterpillar will outgrow its shell four times. The fifth time the caterpillar disappears and becomes a chrysalis. After about 10 days in the chrysalis a butterfly with four delicate wings is born.
But why is the Monarch butterfly special? It’s because every year, one hundred million of them make an astonishing migration and each Monarch on its own flies about 3,200 kms from Canada and Northern America arriving in Mexico to spend the winter. Only Canadian and North American Monarchs travel this distance to avoid certain death from the cold. The cycle starts with a group of Monarchs leaving Mexico at the end of winter. That first generation survives two months migrating up north from Mexico to Texas and Oklahoma where they mate and die. Their progeny, the second and third generation, over the following months, return to the northern parts of the US and Canada in each case surviving only about one month. The fourth generation however is quite special. They live up to nine months and just hours to days after their birth make an epic journey back down to the mountains of Mexico to spend the winter, thus completing this amazing natural phenomenon that eludes explanation.
What triggers this mass exodus from Canada? The young hatchling butterflies recognise landmarks, follow the sun, or sense the earth’s magnetic field and make their trip. It is unclear how they physically do this given that the Monarch’s wingspan is 3½ to 4 inches and weighs about a fifth of an ounce! They only fly when conditions are perfect. If it’s too cold they get sluggish and can’t flap their wings, if it’s too hot they don’t fly because they’d get over heated and they stop often for nectar. The butterflies use the thermal hot air and the wind to carry them: in other words they soar, which doesn’t cost them any energy.
They ultimately make it to the trees in the mountains of Mexico in millions. The tree bark puts heat through their bodies keeping them warm. This feat of survival is something even humans are incapable of, yet this tiny and beautiful creature has mastered it over millennia of practice.
The writer is a Ph.D. in Molecular Genetics and Geno-mics and is working on skin cancer at Novartis