With about 300 species of distinct butterflies, the Danaidae butterfly inhabits both temperate and tropical forest. There are butterflies of every hue and size among them. The Painted Lady, the Purple Crow of Taiwan, the Dark Blue Tiger of Asia and many others paint fluttering color on exotic skies. All have specific routes and obstacles, such as monsoon rains and dry periods, to tackle.
The most famous of the Danaidae is the popular and beautiful Monarch butterfly. And of several migration routes, including those in Asia, Australia and India, none is more well-known than the long-distance migration of the North American Monarch. Some summer as far north as Canada. Many are in the U.S.A. from East to West Coast. The Monarchs cannot stay so far north, however. They need to over-winter far to the south in order to avoid freezing temperatures. Some over-winter in Southern California, but more progress to Mexico.
The butterflies congregate in the same protected areas year after year. They fly through a route over central Texas called the flyway. When they arrive in Mexico, they make their way to one particular high-elevation forest known as the Oyamel Fir forest. Here they find the last unique habitat in the world that they need in order to feed, mate, give birth and send the final travelers back to the far north.
The migration is inter-generational. Three to four generations of butterflies make the trip in separate legs. Many just live and travel for 2-4 months. But the fourth generation, called the Methuselah generation, lives up to 9 months in order to make the longest leg of the trip which is the journey north.
It astounds and amazes all who witness this unique inter-generational trip. Without ever having a single individual or leader who has come this way before, the Monarchs somehow know precise routes, day lengths, food sources and flying conditions.
The migration is long. From between 2,000 and 3,000 miles, these tiny creatures master air currents and long stretches of open water and territory. Most average about 80 miles per day, roosting at night and congregating for warmth.
The vegetation and flying conditions are critical to the survival of this species. They feed primarily upon Milkweed flowers. As the days grow longer, northern stretches of forest and meadow fill with the flowers which precede the oncoming butterflies as they continue to work their way along. The Milkweed and Golden Rod flower supply the nectar and lipids that each butterfly needs to fuel his or her flight.
Human activities such as deforestation, pesticides, mono-culture crops and more impact butterfly migrations. Climate change too will affect butterflies, just as it does all of nature’s cycles and organisms. Storms of rain or cold, wildfires and winds, as well as predators, can also kill them. Sandstorms and low food and water supplies take their toll. Still, with up to 300 million of them determined to brave the journey, enough complete each step to ensure more generations to come, so long as their routes are protected.
Butterflies are solar-powered in that they are able to store and reflect light in honey-comb scales upon their wings. They know also how to detect polarized light and read the low and high sun rays for cues. Enroute, the magnetite in their wings is thought to help steer them through the Sierra Gorda Natural Reserve, which is where several magnetism-rich trans-volcanic mountains stretch below the fluttering cloud. Scientists track a few of the butterflies with tiny wing scribbles to identify their origin and final destination.
Their over-wintering place is in the Oyamel Fir forest, 100 miles west of Mexico City. In this environment, it is believed the Monarchs can stay warm due to the thermal warmth advantage of these fir trunks and flexible leaf needles for perching. Illegal logging is a great threat to them here, so conservationists continue to make efforts to protect the migrations.
A butterfly is not usually thought of as an icon of extreme strength and intelligence. Nor are they celebrated as being extraordinarily tough. But these “floating flowers” are anything but delicate. With a body weighing only a gram and with a brain the size of a pin point, this incredible feat of navigation and aviation is accomplished year after year with the Danaidae Milkweed Butterfly, the true monarch of the skies.