Monarch butterflies might be beautiful, but they are also tough. The migration of monarchs takes them from Canada to central Mexico, and the journey is so long that it outlasts a monarch’s lifetime. So along the way the butterflies lay eggs, and it is a multigenerational effort to make the trip. That is incredible in its own way, but it’s not the most amazing thing about this journey.
As part of their journey, the monarch butterflies fly across Lake Superior. Of course, since this is a body of water this part of the journey must be done in one unbroken flight. That is already a big ask, but the butterflies make it even harder for themselves. They fly south across the lake, then at one point they all turn east, fly east for a while, and then turn back to the south.
There is no obvious survival advantage in doing this, so why do the butterflies all do it?
A common theory among biologists and geologists is that at one point in the past there was a mountain rising out of Lake Superior, possibly one of the highest mountains to have existed on the North American continent. When the mountain was there it would have been impossible for the butterflies to fly over it, so they flew around it.
Now, although the mountain is long gone, the butterflies carry a genetic memory that directs them to fly around it. It is a behaviour that tantalises speculation. How strong is the power of collective inherited memory that it will override what the senses might communicate? It invites the question too as to which is more permanent, the endlessly replicating butterfly or the stony mountain?
It invites the question too as to which is more permanent, the endlessly replicating butterfly or the stony mountain?
