The Monarch mystery

"The Incredible Journey of the Butterflies" is a Nova documentary about the iconic Monarch butterfly and its strange journeys across the North American continent.

The "eastern" population of Monarchs migrates to a relatively small area in central Mexico, the Monarch Butterfly Biosphere Reserve, where they spend the winter. In the spring, the Monarchs return northwards. Curiously, the back journey takes three or four generations, with each succeeding generation somehow "knowing" where to migrate. The last generation in the cycle knows that they should fly southwards to Mexico again! Apparently, these insects can navigate using the position of the sun or perhaps magnetic fields. How the migration route is inherited by subsequent generations is, of course, an interesting question... (The "western" population migrates to southern California, but this is not mentioned in the documentary.)

The documentary doesn't just show us the actual butterflies, but also gives us glimpses of their cultural significance. In Mexico, the local population regards (or used to regard) the Monarchs as the returning spirits of the ancestors, perhaps because the Monarch in-migration coincides with the traditional celebration known as "The Day of the Dead". The relatively poor locals also earn extra money during the Monarch ingathering, by selling souvenirs, renting room for tourists, etc. Unfortunately, the Monarch reserve is threatened by illegal logging operations. Although the WWF pays locals to protect the forest, this has proven more or less impossible, since the illegal loggers are often armed and dangerous. (The sole illegal logger interviewed on the show claims that he is simply trying to survive.)

The documentary also shows the cultural impact of the Monarch in the United States, where children are hired to band the large butterflies for scientific research programs. The entomologists studying the Monarchs virtually worship the creature. One aspect not mentioned (it's a Nova documentary, after all) is the creationist/ID interest in Monarchs, obvious on Youtube, where every other thread dealing with Monarchs and other butterflies seem to be about God or religion!

"The Incredible Journey of the Butterflies" is a good introduction to "Danaus plexippus", and I therefore give it four stars.