It’s that time of the year again. Species of all varieties are packing up and leaving for their winter quarters. The whole science of migratory behavior is mysterious as well as fascinating. The sheer scale of the movement is mind-bobbling. Artic terns fly ten thousand miles or more. Tiny hummingbirds cross hundreds of miles of open oceans to reach warmer climes. The fact that they do it is astounding and the precision of their navigation is no less amazing. The survival of their kind is dependent on the accuracy of their journey.
The monarch butterfly is among the most spectacular. The life cycle of the monarch is complicated and there are four generations involved in each year. Three generations of the monarchs live about three months, but the fourth generations which come to maturity in the fall live about nine months. This lengthening of their life enables them to make the thousands of mile flight from the northeast United States to a tiny patch of oyamel fir trees in northeastern Mexico. Millions upon millions winter in a concentration that brings hordes of tourists to the Mexican mountains each winter. After months of hibernation, they will start a return flight north, but on reaching Texas they will lay their eggs then die. The hatchlings will start their three month life with the long flight to the northeast.
But all is not well with the migration and the reasons are many. The oyamel fir trees are being cut down by the natives who sell them for construction, leaving fewer trees for hibernation. With fewer trees, the tourist trade has been affected which has led to violence between the illegal timber poachers and the locals who are protecting the habitat for the tourist trade. An additional hazard for monarch survival is one about which little has been heard: capturing of butterflies for collectors. Monarchs, in addition to the many colorful species found in Central America, are caught by professional butterfly hunters and sold at amazing prices to those who are collectors.
At the northern end of the migration route climate warming has been blamed for the decrease in migrating monarchs. The fall in temperature is thought to be a trigger for the southern journey but the instinctual behavior is probably more complex than that. Those who follow the migration trends are concerned that the species may be endangered.
It is easy to look at a problem from one point of time and generalize to explanations that may be too broad. Particularly suspect to that danger is this matter of climate change. This year the temperature in the northeast has been unseasonably high accompanied by unusually strong winds from the south. The monarchs may not be able to navigate the southwestern course they instinctively fly because of the high winds or they may not realize that the time to move south is at hand. Whatever the reason, if the migration is scant, then the generation that lives to migrate and then propagate will be similarly reduced.
Given the magnitude of the problems we face in the world, one might legitimately shrug the shoulders and not give a thought to these insects’ challenges. We are all connected, even to the bugs with whom we share the planet. The human propensity to migrate to Florida for the winter will not be marginalized but one might give thought to the carbon footprint that may in the next century lay its heavy boot on far more than the stately monarch butterfly.